Wednesday, December 16, 2015

Basic practice problems



1.  Light hits a piece of plastic at an angle of 50 degrees (with respect to normal).  If the angle of refraction inside is 25 degrees, what is the index of refraction of this plastic?  Also, what is the speed of light inside the plastic.

2.  What is the frequency of light with a wavelength of 100 nm in air (where it travels pretty much at the speed of light).  (That's 100 x 10^-9 m.)

3.  A lens has a focal length of -25 cm.  A candle is 10 cm in front of it.  Find the following:

a.  type of lens
b.  location of image (di)
c.  type of image
d.  magnification of image
e.  whether image is up or down
f.  whether image is real or virtual


Answers

1. 
1.8
1.66 x 10^8 m/s

2. 3 x 10^15 Hz
  

3.  concave, -7.1 cm = di (making it virtual), mag = -0.7  (which makes it smaller and upside-down)

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