Will Changing Light Color Affect Refraction and Photoelectric Emission?

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Changing the color of incident light from green to red at a constant angle will affect the refracted angle due to the different refractive indices for each color, as described by Snell's law. The speed of green light in glass can be calculated using the formula n = c/v, resulting in approximately 214,285,714.3 m/s. For photoelectric emission, the threshold wavelength can be determined from the work function, with wavelengths longer than this threshold resulting in no emission, while shorter wavelengths will cause emission. The kinetic energy of an ejected electron from sodium can be calculated using the energy of the incident light minus the work function, indicating that if the energy is less than the work function, the electron cannot be emitted. Understanding these concepts is essential for solving the posed physics problems effectively.
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Homework Statement


I've got a couple so I'm going to keep them all within this thread.

1) A ray of green light is incident in air on a flat glass surface, at an angle of 45 degrees measured from the normal. The glass has a refractive index of 1.4 for this green light.

(a) if the color of th eincident light is changed from green to red, the incident angle staying the same, will the refracted angle change? Explain
(b) What is the speed of the green light in the glass?

2) A certain metal has a work function of 3eV.
(a) What is the threshold wavelength to cause photoelectric emission in this metal?
(b) For a light of wavelength longer/shorter than the threshold, incident on this metal, what happens?

3) Sodium has a work function of 2.28eV. What is the kinetic energy of an electron ejected from sodium where it is illuminated by light of wavelength
(i) 410nm
(ii) 550nm

The Attempt at a Solution



Physics is far from my forte and I have a feeling 1b, 2b and 3 are all a matter of using a simple formula. However I was unable to find any relevant equations. I'm also unsure of the theory behind 1a and 2a so if somebody could explain that too it would be much appreciated! :blushing:
 
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For the first question look up Snell's law. For the others, start by looking up the Photoelectric Effect.
 
The only version of Snell's I am familiar with is this one:

f97a84e79cf42d848f659857ca5d0ffc.png


But I can't see how that's related to speed of light...
 
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For the speed part consider

n = c/v

where n is the index of refraction, c is the speed of light in a vacuum, and v is the speed of light in a medium.
 
hage567 said:
For the speed part consider

n = c/v

where n is the index of refraction, c is the speed of light in a vacuum, and v is the speed of light in a medium.

I knew it was something basic...:smile:

n=1.4, c=3*10^8

hence v=214285714.3m/s
 
for question 3 (ii) my value of hf is less than that of W, thus resulting in a negative value for Kinetic energy. Does this mean that the energy of the wavelength is not enough to overcome the work function of the metal and hence the electron is unable to leave the surface?
 

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