E2science

Depth perception is the mechanism in the human visual system which disambiguates the relative positions of two three-dimensional objects.

The visual system relies on both physiological and psychological cues to make accurate estimates of the depths of objects.

Physiological depth cues are formed by keeping track of the muscular adjustments the visual system makes. It's hard to establish just how much these cues contribute to depth perception, but they are assumed to be weak. They include the following:

• Accommodation - The change in the focal length of the crystalline lens in the eyes. This is a monocular cue.
• Convergence - Rotation of the eyeballs so that the directions of the gaze of the eyes intersects at the point of interest. This is a binocular cue.

Psychological depth cues are based on the analysis of the image on the retina by the visual cortex of the brain. They are usually much stronger than the physiological depth cues.

The following two psychological depth cues are based on parallax, which is the difference in the appearance of an object caused by a difference in viewpoint.

• Binocular Disparity - The difference in the positions of the same object in images viewed by the left and right eyes. Binocular disparity is the result of binocular parallax, which is the difference between the images viewed by the two eyes.
• Motion Parallax - A monocular cue that relies on the changes in the images viewed in an eye as the viewer moves.

Physiological and parallax depth cues are effective in perceiving depth of only objects near the viewer. This is because the farther away an object is, the larger the distance to the object is in comparison to the interocular distance or the distance moved by the viewer (in the case of motion parallax). For this reason, accommodation is effective only up to about 2 meters, and convergence up to about 10 meters.

The remaining psychological depth cues are based on the appearance of the object from one viewpoint. They are monocular cues, independent of parallax. They are effective at all distances and are the predominant depth cues for distant objects.

• Linear Perspective - The sizes of objects change in inverse proprotion to their depth. Objects which are farther appear smaller than objects which are closer. We compare the retinal image size of the object with the known size of object to judge how far it is. Furthermore, objects on the ground which are seen higher in the visual field are perceived to be farther. Similarly, objects in the sky which are seen lower in the visual field are perceived to be farther.
• Occlusion - If an object overlaps another, we perceive the blocker as being closer.
• Aerial Perspective - Objects which are far away often appear hazy or bluish. This is due to the atmospheric scattering of light.
• Texture Gradient - Textures on an object appear coarse if the object is close to the viewer, and fine if the object is far from the viewer.
• Shading and Shadowing - Known properties of surfaces and mechanisms of reflection are used by the visual system to estimate the orientation and shape of objects. Knowledge of the location of light sources helps us determine location of objects from their shadows.
• Chromostereopsis - Chromatic Aberration in the eyes results in objects colored with some wavelengths of light to appear closer or farther than objects colored with some other wavelength.

Since the majority of depth cues are monocular, vision loss in one eye does not result in the loss of the ability to perceive depth. In fact, only two depth cues -- convergence and binocular disparity -- require both eyes to operate. Therefore, loss of stereoscopic vision affects depth perception only near the viewer -- and even there, other cues make up for it to a great extent.

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A biosurfactant is a natural surfactant: a chemical produced by a living organism that decreases the surface tension of water.

For instance, biosurfactants on the lungs of human babies and late-term fetuses keep their lungs from collapsing. Fetuses start producing lung surfactant in their last trimester.

Earlier-term fetuses have trouble surviving in part because their lungs tend to collapse due to the surface tension of water on their alveoli prevents them from expanding after the infant has exhaled. The medical name for this problem is respiratory distress syndrome (RDS). In 1990, the U.S. Food and Drug Administration approved a form of surfactant therapy that has saved the lives of many premature infants.

One of the surfactant agents for premature infants is marketed under the name Exosurf Neonatal. It comes as a powder that physicians mix with water and blow into the babies' lungs.

Other biosurfactants, which are often rhamnolipids, are used for a wide variety of industrial applications. They are sometimes produced by engineered bacteria and are used as emulsifiers and solvents in:

• hydrocarbon recovery
• concrete
• soil washing
• metal processing
• leather processing
• lubricants
• pulp and paper processing
• textiles
• detergents
• foods
• inks
• paints
• adhesives
• personal hygiene products
• agricultural adjuvants
• water treatment (especially removing metals from wastewater)
• pharmaceuticals
• cosmetics
• ophthalmic products

You have an older relative who calls, and they are short of breath. They have a wet cough. You take them to the emergency room and the doctors and staff do a lot of tests. You think that they must have pneumonia, because they can't breathe and are coughing. The doctor says that your relative will be hospitalized. The doctors talk about pneumonia but then later on they say, no, it is congestive heart failure. It is not a heart attack. You wonder why a heart problem shows up in the lungs.

Heart failure, or congestive heart failure, is a confusing name for an illness. Heart failure is uncommon among the young but becomes more and more common as people age. Understanding heart failure starts by remembering that the heart is a pump. Heart failure means the heart is not pumping right. What happens when a pump is failing?

"Something backs up," reply my patients. "Something floods."

Exactly! And where is the flooding? This depends on what part of the heart pump is not working. The heart has four chambers. The right side of the heart pumps blood in to the lungs, to pick up oxygen. The oxygenated blood goes to the left heart. The left side of the heart pumps blood to everything else: heart, brain, body, kidneys, organs, skin and so forth. Then the blood returns through veins to the right heart to pick up oxygen again.

With right sided heart failure, the blood backs up into the body. With left sided heart failure the blood backs up in to the lungs. Both can occur, so that the whole system is sluggish.

What causes heart failure? The two most common causes are coronary artery disease and hypertension. Coronary artery disease is partially blocked arteries that are supposed to take oxygen and nutrition to the heart. If the arteries are partially blocked, the heart muscle cannot get enough oxygen or nutrition and can't pump well. If the artery is fully blocked, that part of the heart muscle can die: that is a heart attack, or myocardial infarction. Hypertension is high blood pressure. If the heart pump is always pumping against high pressure, what does it do? The wall of the heart thickens, the muscle getting thicker. We think bigger muscles are better, but they aren't always. When the wall of the left heart thickens too much, the amount of blood that the heart can pump with each beat drops. Normally, the left heart pumps 55-70% of the blood into the body with each beat. In heart failure, the amount drops. If the left heart can only pump 20%, this is clearly bad. Some mild heart changes are normal with aging: as people reach their 70s and 80s, there is usually some right sided mild heart pump failure. This is not usually a problem. There are other more rare causes of heart failure and it can happen to someone young.

What are the symptoms of heart failure? If the right heart, that pumps to the lungs, is not pumping well, blood backs up in the body. Usually in the legs, because over time gravity and the pooling of blood cause swelling. The swelling can be enormous and frightening. If the left heart backs up, the lungs have too much fluid. The body tries to cope with this and there is often fluid backed up in the legs as well.

How do we prevent heart failure? Stay as healthy as possible, avoid coronary artery disease, and have your blood pressure checked yearly. I see people who boast that they have not seen a doctor for twenty years. If they have had high blood pressure for 15 of those years, the damage may already be done to their heart. We all know the recommendations for avoiding coronary artery disease and heart attacks: don't smoke or stop smoking, exercise, eat a diet high in whole grains and vegetables and low in fat and sweets, drink small amounts or no alcohol, avoid being overweight, and drugs like cocaine and methamphetamines can have bad heart effects as well.

"But doctor, I've lived a healthy life and now you say my blood pressure is high?" Yes, the high blood pressure experts say that 90% of people in the United States will develop high blood pressure. Sometimes not until age 90, but most people will! With exercise, not smoking, a healthy diet and so forth, you can delay this as long as possible: but when your doctor tells you your blood pressure is high, take your medicine. Then you delay heart failure!

How do medicines for heart failure work? There are many medicines that can help with heart failure. Diuretics, such as HCTZ and lasix, remove extra fluid through the kidneys and both lower blood pressure and the amount of fluid backing up the system. Beta blockers, like atenolol and propranolol, help the heart to pump more strongly and lower blood pressure. Calcium channel blockers, like diltiazem, also work on the heart muscle and lower blood pressure. If the cause is coronary artery disease, nitrates help to keep the arteries open and aspirin helps keep clots from forming.

If I have heart failure, what else can I do besides take medicine? Again, stop smoking and so forth. Eating salt can make heart failure worse, because the salt tends to keep the kidneys from removing fluid. If your doctor recommends a low salt diet, avoiding the potato chips and most canned soups and using less salt will all help. When someone's heart failure is getting out of control, their weight increases as fluid backs up: so get a good scale, know your goal weight and contact your doctor if you have a sudden weight gain, 4-5 pounds within a couple of days. The other big symptom is shortness of breath and a wet cough, if fluid is backing up in the lungs. Know when to ask for help.

This appeared in The Peninsula Daily News Healthy Living section, June, 2010.
For Science Quest 2012.

An enteric coating is a coating put on a pill or capsule so that it doesn't dissolve until it reaches the small intestine. While the coating may make a pill easier to swallow and will mask bitter-tasting medicine, enteric coatings are primarily used because the drug is likely to cause stomach irritation or because its effectiveness might be reduced by stomach acids or enzymes.

Enteric coatings work because they are selectively insoluble substances -- they won't dissolve in the acidic juices of the stomach, but they will when they reach the higher pH of the small intestine.

Most enteric coatings won't dissolve in solutions with a pH lower than 5.5. Commonly-used enteric coatings may be made from:

• methacrylic acid copolymers
• cellulose acetate (and its succinate and phthalate version)
• styrol maleic acid co-polymers
• polymethacrylic acid/acrylic acid copolymer
• hydroxypropyl methyl cellulose phthalate
• polyvinyl acetate phthalate
• hydroxyethyl ethyl cellulose phthalate
• hydroxypropyl methyl cellulose acetate succinate
• cellulose acetate tetrahydrophtalate
• acrylic resin
• timellitate
• shellac

Most enteric coatings are dissolved in organic solvents such as acetone, methanol, ethanol, isopropyl alcohol, ethyl acetate, methylene chloride, etc. and applied to the tablets or capsules. The coatings might be sprayed on or applied as a chemical vapor, or the tablets might be put in a rotating pan partially filled with the coating. The solvent evaporates, leaving the coating behind.

It is worth noting that some enteric coatings are essentially plastics, and some are phthalates. Certain phthalates have been associated with cancer and birth defects and are suspected endocrine disruptors. There is no data on whether the type and amount of chemicals used as enteric coatings could present a health risk. Such data is not likely to be forthcoming soon.

All Nobel Prize winners in Physics up through 2011 are listed below, in addition to the Nobel Prize's committee's reason for awarding the prize. This is a mini-history of physics since the beginning of the epochal 20^th century. Each year is linked to Stockholm speeches, which gives great insight into the methods of science research. Any student of physics will find them fascinating reading.

• 2012, Serge Haroche and David J. Wineland, "for ground-breaking experimental methods that enable measuring and manipulation of individual quantum systems"
• 2011, Saul Perlmutter, Brian P. Schmidt, Adam G. Riess, "for the discovery of the accelerating expansion of the Universe through observations of distant supernovae"
• 2010, Andre Geim, Konstantin Novoselov, ”for groundbreaking experiments regarding the two-dimensional material graphene"
• 2009, Charles Kuen Kao, Willard S. Boyle, George E. Smith, Kao: "for groundbreaking achievements concerning the transmission of light in fibers for optical communication", Boyle & Smith: "for the invention of an imaging semiconductor circuit – the CCD sensor"
• 2008, Yoichiro Nambu, Makoto Kobayashi, Toshihide Maskawa, Nambu "for the discovery of the mechanism of spontaneous broken symmetry in subatomic physics", Kobayashi and Maskawa "for the discovery of the origin of the broken symmetry which predicts the existence of at least three families of quarks in nature"
• 2007, Albert Fert, Peter Grünberg, "for the discovery of Giant Magnetoresistance"
• 2006, John C. Mather, George F. Smoot, "for their discovery of the blackbody form and anisotropy of the cosmic microwave background radiation"
• 2005, Roy J. Glauber, John L. Hall, Theodor W. Hänsch, Glauber "for his contribution to the quantum theory of optical coherence", Hall and Hänsch "for their contributions to the development of laser-based precision spectroscopy, including the optical frequency comb technique"
• 2004, David J. Gross, H. David Politzer, Frank Wilczek, "for the discovery of asymptotic freedom in the theory of the strong interaction"
• 2003, Alexei A. Abrikosov, Vitaly L. Ginzburg, Anthony J. Leggett, "for pioneering contributions to the theory of superconductors and superfluids"
• 2002, Raymond Davis Jr., Masatoshi Koshiba, Riccardo Giacconi, Davis and Koshiba "for pioneering contributions to astrophysics, in particular for the detection of cosmic neutrinos]" and Giacconi "for pioneering contributions to astrophysics, which have led to the discovery of cosmic X-ray sources"
• 2001, Eric A. Cornell, Wolfgang Ketterle, Carl E. Wieman, "for the achievement of Bose-Einstein condensation in dilute gases of alkali atoms, and for early fundamental studies of the properties of the condensates"
• 2000, Zhores I. Alferov, Herbert Kroemer, Jack S. Kilby, "for basic work on information and communication technology" to Alferov and Kroemer "for developing semiconductor heterostructures used in high-speed- and opto-electronics" and Kilby "for his part in the invention of the integrated circuit"
• 1999, Gerardus 't Hooft, Martinus J.G. Veltman, "for elucidating the quantum structure of electroweak interactions in physics"
• 1998, Robert B. Laughlin, Horst L. Störmer, Daniel C. Tsui, "for their discovery of a new form of quantum fluid with fractionally charged excitations"
• 1997, Steven Chu, Claude Cohen-Tannoudji, William D. Phillips, "for development of methods to cool and trap atoms with laser light"
• 1996, David M. Lee, Douglas D. Osheroff, Robert C. Richardson, "for their discovery of superfluidity in helium-3"
• 1995, Martin L. Perl, Frederick Reines, "for pioneering experimental contributions to lepton physics", Perl "for the discovery of the tau lepton" and Reines "for the detection of the neutrino"
• 1994, Bertram N. Brockhouse, Clifford G. Shull, "for pioneering contributions to the development of neutron scattering techniques for studies of condensed matter", Brockhouse "for the development of neutron spectroscopy" and Shull "for the development of the neutron diffraction technique"
• 1993, Russell A. Hulse, Joseph H. Taylor Jr., "for the discovery of a new type of pulsar, a discovery that has opened up new possibilities for the study of gravitation"
• 1992, Georges Charpak, "for his invention and development of particle detectors, in particular the multiwire proportional chamber"
• 1991, Pierre-Gilles de Gennes, "for discovering that methods developed for studying order phenomena in simple systems can be generalized to more complex forms of matter, in particular to liquid crystals and polymers"
• 1990, Jerome I. Friedman, Henry W. Kendall, Richard E. Taylor, "for their pioneering investigations concerning deep inelastic scattering of electrons on protons and bound neutrons, which have been of essential importance for the development of the quark model in particle physics"
• 1989, Norman F. Ramsey, Hans G. Dehmelt, Wolfgang Paul, Ramsey "for the invention of the separated oscillatory fields method and its use in the hydrogen maser and other atomic clocks", and to Dehmelt and Paul "for the development of the ion trap technique"
• 1988, Leon M. Lederman, Melvin Schwartz, Jack Steinberger, "for the neutrino beam method and the demonstration of the doublet structure of the leptons through the discovery of the muon neutrino"
• 1987, J. Georg Bednorz, K. Alexander Müller, "for their important break-through in the discovery of superconductivity in ceramic materials"
• 1986, Ernst Ruska, Gerd Binnig, Heinrich Rohrer, Ruska "for his fundamental work in electron optics, and for the design of the first electron microscope", Binnig and Rohrer "for their design of the scanning tunneling microscope"
• 1985, Klaus von Klitzing, for the discovery of the quantized Hall effect"
• 1984, Carlo Rubbia, Simon van der Meer, "for their decisive contributions to the large project, which led to the discovery of the field particles W and Z, communicators of weak interaction"
• 1983, Subramanyan Chandrasekhar, William Alfred Fowler, Chandrasekhar "for his theoretical studies of the physical processes of importance to the structure and evolution of the stars" and Fowler "for his theoretical and experimental studies of the nuclear reactions of importance in the formation of the chemical elements in the universe"
• 1982, Kenneth G. Wilson, "for his theory for critical phenomena in connection with phase transitions"
• 1981, Nicolaas Bloembergen, Arthur Leonard Schawlow, Kai M. Siegbahn, Bloembergen and Schawlow "for their contribution to the development of laser spectroscopy" and Siegbahn "for his contribution to the development of high-resolution electron spectroscopy"
• 1980, James Watson Cronin, Val Logsdon Fitch, "for the discovery of violations of fundamental symmetry principles in the decay of neutral K-mesons"
• 1979, Sheldon Lee Glashow, Abdus Salam, Steven Weinberg, "for their contributions to the theory of the unified weak and electromagnetic interaction between elementary particles, including, inter alia, the prediction of the weak neutral current"
• 1978, Pyotr Leonidovich Kapitsa, Arno Allan Penzias, Robert Woodrow Wilson, Kapitsa "for his basic inventions and discoveries in the area of low-temperature physics", and to Penzias and Wilson "for their discovery of cosmic microwave background radiation"
• 1977, Philip Warren Anderson, Sir Nevill Francis Mott, John Hasbrouck van Vleck, "for their fundamental theoretical investigations of the electronic structure of magnetic and disordered systems"
• 1976, Burton Richter, Samuel Chao Chung Ting, "for their pioneering work in the discovery of a heavy elementary particle of a new kind"
• 1975, Aage Niels Bohr, Ben Roy Mottelson, Leo James Rainwater, "for the discovery of the connection between collective motion and particle motion in atomic nuclei and the development of the theory of the structure of the atomic nucleus based on this connection"
• 1974, Sir Martin Ryle, Antony Hewish, "for their pioneering research in radio astrophysics: Ryle for his observations and inventions, in particular of the aperture synthesis technique, and Hewish for his decisive role in the discovery of pulsars"
• 1973, Leo Esaki, Ivar Giaever, Brian David Josephson, Esaki and Giaever "for their experimental discoveries regarding tunneling phenomena in semiconductors and superconductors, respectively" and Josephson "for his theoretical predictions of the properties of a supercurrent through a tunnel barrier, in particular those phenomena which are generally known as the Josephson effects"
• 1972, John Bardeen, Leon Neil Cooper, John Robert Schrieffer, "for their jointly developed theory of superconductivity, usually called the BCS-theory"
• 1971, Dennis Gabor, "for his invention and development of the holographic method"
• 1970, Hannes Olof Gösta Alfvén, Louis Eugène Félix Néel, Alfvén "for fundamental work and discoveries in magnetohydrodynamics with fruitful applications in different parts of plasma physics" and Néel "for fundamental work and discoveries concerning antiferromagnetism and ferrimagnetism which have led to important applications in solid state physics"
• 1969, Murray Gell-Mann, "for his contributions and discoveries concerning the classification of elementary particles and their interactions"
• 1968, Luis Walter Alvarez, "for his decisive contributions to elementary particle physics, in particular the discovery of a large number of resonance states, made possible through his development of the technique of using hydrogen bubble chamber and data analysis"
• 1967, Hans Albrecht Bethe, "for the discovery and development of optical methods for studying Hertzian resonances in atoms"
• 1966, Alfred Kastler, "for the discovery and development of optical methods for studying Hertzian resonances in atoms"
• 1965, Sin-Itiro Tomonaga, Julian Schwinger, Richard P. Feynman, "for their fundamental work in quantum electrodynamics, with deep-ploughing consequences for the physics of elementary particles"
• 1964, Charles Hard Townes, Nicolay Gennadiyevich Basov, Aleksandr Mikhailovich Prokhorov, "for fundamental work in the field of quantum electronics, which has led to the construction of oscillators and amplifiers based on the maser-laser principle"
• 1963, Eugene Paul Wigner, Maria Goeppert Mayer, J. Hans D. Jensen, Wigner "for his contributions to the theory of the atomic nucleus and the elementary particles, particularly through the discovery and application of fundamental symmetry principles", and Mayer and Jensen "for their discoveries concerning nuclear shell structure"
• 1962, Lev Davidovich Landau, "for his pioneering theories for condensed matter, especially liquid helium"
• 1961, Robert Hofstadter, Rudolf Ludwig Mössbauer, Hofstadter "for his pioneering studies of electron scattering in atomic nuclei and for his thereby achieved discoveries concerning the structure of the nucleons" and Mössbauer "for his researches concerning the resonance absorption of gamma radiation and his discovery in this connection of the effect which bears his name"
• 1960, Donald Arthur Glaser, "for the invention of the bubble chamber"
• 1959, Emilio Gino Segrè, Owen Chamberlain, "for their discovery of the antiproton"
• 1958, Pavel Alekseyevich Cherenkov, Il´ja Mikhailovich Frank, Igor Yevgenyevich Tamm, "for the discovery and the interpretation of the Cherenkov effect"
• 1957, Chen Ning Yang, Tsung-Dao (T.D.) Lee, "for their penetrating investigation of the so-called parity laws which has led to important discoveries regarding the elementary particles"
• 1956, William Bradford Shockley, John Bardeen, Walter Houser Brattain, "for their researches on semiconductors and their discovery of the transistor effect"
• 1955, Willis Eugene Lamb, Polykarp Kusch, Lamb: "for his discoveries concerning the fine structure of the hydrogen spectrum" and Kusch "for his precision determination of the magnetic moment of the electron"
• 1954, Max Born, Walther Bothe, Born: "for his fundamental research in quantum mechanics, especially for his statistical interpretation of the wavefunction" and Bothe: "for the coincidence method and his discoveries made therewith"
• 1953, Frits (Frederik) Zernike, "for his demonstration of the phase contrast method, especially for his invention of the phase contrast microscope"
• 1952, Felix Bloch, Edward Mills Purcell, "for their development of new methods for nuclear magnetic precision measurements and discoveries in connection therewith"
• 1951, Sir John Douglas Cockcroft, Ernest Thomas Sinton Walton, "for their pioneer work on the transmutation of atomic nuclei by artificially accelerated atomic particles"
• 1950, Cecil Frank Powell, for his development of the photographic method of studying nuclear processes and his discoveries regarding mesons made with this method"
• 1949, Hideki Yukawa, "for his prediction of the existence of mesons on the basis of theoretical work on nuclear forces"
• 1948, Patrick Maynard Stuart Blackett, "for his development of the Wilson cloud chamber method, and his discoveries therewith in the fields of nuclear physics and cosmic radiation"
• 1947, Sir Edward Victor Appleton, "for his investigations of the physics of the upper atmosphere especially for the discovery of the so-called Appleton layer"
• 1946, Percy Williams Bridgman, "for the invention of an apparatus to produce extremely high pressures, and for the discoveries he made therewith in the field of high pressure physics"
• 1945, Wolfgang Pauli, "for the discovery of the Exclusion Principle, also called the Pauli Principle"
• 1944, Isidor Isaac Rabi, "for his resonance method for recording the magnetic properties of atomic nuclei"
• 1943, Otto Stern, "for his contribution to the development of the molecular ray method and his discovery of the magnetic moment of the proton"
• 1942-1940, No Nobel Prize was awarded this year. The prize money was with 1/3 allocated to the Main Fund and with 2/3 to the Special Fund of this prize section.
• 1939, Ernest Orlando Lawrence, "for the invention and development of the cyclotron and for results obtained with it, especially with regard to artificial radioactive elements"
• 1938, Enrico Fermi, "for his demonstrations of the existence of new radioactive elements produced by neutron irradiation, and for his related discovery of nuclear reactions brought about by slow neutrons"
• 1937, Clinton Joseph Davisson, George Paget Thomson, "for their experimental discovery of the diffraction of electrons by crystals"
• 1936, Victor Franz Hess, Carl David Anderson, Hess: "for his discovery of cosmic radiation" and Anderson: "for his discovery of the positron"
• 1935, James Chadwick, "for the discovery of the neutron"
• 1934, No Nobel Prize was awarded this year. The prize money was with 1/3 allocated to the Main Fund and with 2/3 to the Special Fund of this prize section.
• 1933, Erwin Schrödinger, Paul Adrien Maurice Dirac, "for the discovery of new productive forms of atomic theory"
• 1932, Werner Karl Heisenberg, "for the creation of quantum mechanics, the application of which has, inter alia, led to the discovery of the allotropic forms of hydrogen"
• 1931, No Nobel Prize was awarded this year. The prize money was with 1/3 allocated to the Main Fund and with 2/3 to the Special Fund of this prize section.
• 1930, Sir Chandrasekhara Venkata Raman, "for his work on the scattering of light and for the discovery of the effect named after him".
• 1929, Prince Louis-Victor Pierre Raymond de Broglie, "for his discovery of the wave nature of electrons"
• 1928, Owen Willans Richardson, "for his work on the thermionic phenomenon and especially for the discovery of the law named after him"
• 1927, Arthur Holly Compton, Charles Thomson Rees Wilson, Compton: "for his discovery of the effect named after him" and Wilson: "for his method of making the paths of electrically charged particles visible by condensation of vapour"
• 1926, Jean Baptiste Perrin, "for his work on the discontinuous structure of matter, and especially for his discovery of sedimentation equilibrium"
• 1925, James Franck, Gustav Ludwig Hertz, "for their discovery of the laws governing the impact of an electron upon an atom"
• 1924, Karl Manne Georg Siegbahn, "for his discoveries and research in the field of X-ray spectroscopy"
• 1923, Robert Andrews Millikan, "for his work on the elementary charge of electricity and on the photoelectric effect"
• 1922, Niels Henrik David Bohr, "for his services in the investigation of the structure of atoms and of the radiation emanating from them"
• 1921, Albert Einstein, "for his services to Theoretical Physics, and especially for his discovery of the law of the photoelectric effect"
• 1920, Charles Edouard Guillaume, "in recognition of the service he has rendered to precision measurements in Physics by his discovery of anomalies in nickel steel alloys"
• 1919, Johannes Stark, "for his discovery of the Doppler effect in canal rays and the splitting of spectral lines in electric fields"
• 1918, Max Karl Ernst Ludwig Planck, "in recognition of the services he rendered to the advancement of Physics by his discovery of energy quanta"
• 1917, Charles Glover Barkla, "for his discovery of the characteristic Röntgen radiation of the elements"
• 1916, No Nobel Prize was awarded this year. The prize money was with 1/3 allocated to the Main Fund and with 2/3 to the Special Fund of this prize section.
• 1915,Sir William Henry Bragg, William Lawrence Bragg, "for their services in the analysis of crystal structure by means of X-rays"
• 1914, Max von Laue, "for his discovery of the diffraction of X-rays by crystals".
• 1913, Heike Kamerlingh Onnes, "for his investigations on the properties of matter at low temperatures which led, inter alia, to the production of liquid helium"
• 1912, Nils Gustaf Dalén, "for his invention of automatic regulators for use in conjunction with gas accumulators for illuminating lighthouses and buoys"
• 1911, Wilhelm Wien, "for his discoveries regarding the laws governing the radiation of heat"
• 1910, Johannes Diderik van der Waals, "for his work on the equation of state for gases and liquids"
• 1909, Guglielmo Marconi, Karl Ferdinand Braun, "in recognition of their contributions to the development of wireless telegraphy"
• 1908, Gabriel Lippmann, "for his method of reproducing colours photographically based on the phenomenon of interference"
• 1907, Albert Abraham Michelson, "for his optical precision instruments and the spectroscopic and metrological investigations carried out with their aid"
• 1906, Joseph John Thomson, "in recognition of the great merits of his theoretical and experimental investigations on the conduction of electricity by gases"
• 1905, Philipp Eduard Anton von Lenard, "for his work on cathode rays"
• 1904, Lord Rayleigh (John William Strutt), "for his investigations of the densities of the most important gases and for his discovery of argon in connection with these studies"
• 1903, Antoine Henri Becquerel, Pierre Curie, Marie Curie, née Sklodowska, Becquerel: "in recognition of the extraordinary services he has rendered by his discovery of spontaneous radioactivity", Pierre Curie and Marie Curie, née Sklodowska: "in recognition of the extraordinary services they have rendered by their joint researches on the radiation phenomena discovered by Professor Henri Becquerel"
• 1902, Hendrik Antoon Lorentz, Pieter Zeeman, "in recognition of the extraordinary service they rendered by their researches into the influence of magnetism upon radiation phenomena"
• 1901, Wilhelm Conrad Röntgen, "in recognition of the extraordinary services he has rendered by the discovery of the remarkable rays subsequently named after him"

The site: http://www.nobelprize.org/nobel_prizes/physics/