High school physics. Sixteen. Reflection and refraction of light (geometrical optics)
1. reflection law α = I {α; Reflection angle, I: incident angle}
2. Absolute refractive index (light from vacuum to medium) n = c/v = sin/sin {dispersion of light, red light in visible light has a small refractive index, n: refractive index, c: light speed in vacuum, v: light speed in medium,: incident angle,: refraction angle}.
3. Total reflection: 1) Critical angle C: SINC = 1/n when light enters vacuum or air from medium.
2) Conditions for total reflection: light dense medium is injected into light hydrophobic medium; The incident angle is equal to or greater than the critical angle.
Note: (1) law of reflection imaging of plane mirror: isosceles vertical virtual image, image and object are symmetrical along the plane mirror;
(2) The law of prism refraction imaging: a virtual image is formed, the emergent light deflects to the bottom, and the position of the image deviates to the top;
(3) Optical fiber is the practical application of total reflection of light [see Volume III P 12], magnifying glass is convex lens, and myopia glasses are concave lens;
(4) Memorizing the imaging laws of various optical instruments, and making the optical path diagram by using the law of reflection (refraction) and the reversibility of the optical path is the key to solving the problem;
(5) The dispersion law of white light passing through the prism: see [Volume III P 16] for the purple light emitted near the bottom.
17. the essence of light (light has both particle and fluctuation, which is called wave-particle duality of light)
1. Two theories: particle theory (Newton) and wave theory (Huygens) [see Volume III P23] are not enough.
2. Double-slit interference: there are bright stripes in the middle; Bright stripe position: = n λ; The position of dark stripes: = (2n+ 1) λ/2 (n = 0, 1, 2,3,); Stripe spacing {:optical path difference (optical path difference); λ: the wavelength of light; λ/2: half wavelength of light; D the distance between two slits; L: distance between baffle and screen}
3. The color of light is determined by the frequency of light, which is determined by the light source and has nothing to do with the medium. The propagation speed of light is related to the medium. The order of light color from low frequency to high frequency is: red, orange, yellow, green, blue, indigo and purple (note: purple light has high frequency and low wavelength).
4. Film interference: the thickness of antireflection film is 1/4 of the wavelength of green light in the film, that is, the thickness of antireflection film is d = λ/4 [see Volume III P25].
5. Diffraction of light: Light propagates in a straight line in a homogeneous medium without obstacles. When the size of the obstacle is much larger than the wavelength of light, the diffraction phenomenon of light is not obvious, and it can be considered as propagating along a straight line. On the contrary, it can't be considered as traveling in a straight line [see Volume III P27.
6. Polarization of light: Polarization of light indicates that light is shear wave [see P32 in Volume III.
7. Electromagnetic theory of light: the essence of light is electromagnetic wave. Electromagnetic spectrum (in descending order of wavelength): radio waves, infrared rays, visible light, ultraviolet rays, roentgen rays and gamma rays. Discovery, characteristics, generation mechanism and practical application of infrared rays, ultraviolet rays and linear roentgen rays [see Volume III P29
8. Photon says that the energy of a photon e = h ν {h: Planck constant = 6.63× 10-34j.s, ν: the frequency of light}
9. Einstein's photoelectric effect equation: mvm2/2 = hν-w {mvm2/2: initial kinetic energy of photoelectrons, hν: photon energy, w: work function of metals}.
Note: (1) It is necessary to distinguish the principle, conditions, patterns and applications of light interference and diffraction, such as double-slit interference, thin-film interference, single-slit diffraction, circular hole diffraction and circular screen diffraction.
(2) Other related contents: the development history of light essence theory/Poisson bright spot/emission spectrum/absorption spectrum/spectral analysis/atomic characteristic spectral line [see volume III P50]/ regular photon theory of photoelectric effect [see volume III p 4 1]/ photocell and its application/wave-particle duality of light [see volume III P45]/ laser [see volume III].