a) You observe a beam of light emitted from a spacecraft moving at a speed of c/

Question

a) You observe a beam of light emitted from a spacecraft moving at a speed of c/4 away from
you. What is the speed of the photons with respect to you?
b) Does the momentum of a photon change as it passes between two media with different indices
of refraction? How about its wavelength? Explain.
c) Does the frequency of a photon change as it passes between two media with different indices
of refraction? How about its wavelength? Explain.
d) Calculate the critical angle of incidence for total internal reflection in the case of rays
approaching the boundary surface between diamond (n=2.42) and cedar oil (n=1.6).
e) Explain the difference between a real image and a virtual one.

Explanation / Answer

(a)

same as speed of light

(b)

lamda = h/p

p = h/lamda

yes lamda value changes with refracitve index of medium so momentum and wave lenght changes

(c)

frequency does not change but wave lenght changes with refracitve index

(d)

theta_c= sin^-1 ( 1.6/2.42) = 41.38 degree

(e)

A real image is formed when light rays originating from a point on one side of a lens are refracted by the lens so that they focus to a point on the other side of the lens at the image location. this happens when the object is farther away from the converging lens than the focal lenght

A virtual image is formed when light rays originating from a point on one side of a lens are refracted by the lens so that they diverge on the other side of the lens . when these rays are traced back in a straight line then appear to diverge from a point on the same side of the lens as the object . this happens when the object is closer to converging lens than the focal length.

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