Question

1. In winter a lake has a 0.20m thick ice layer over 1.50m of water. A light beam from above strikes a spot on the ice, making a 29? angle with the normal.

Part A

How far horizontally from that spot does the light ray strike the lake bottom?

2. You

Answer 1

(3)in the third problem,

Apparent depth is given,

d' = 5.3 meters

actual depth has to be calculated.

We know that,

d' = d (n2/n1) which gives us ( n2 and n1 are ref indices of final and initial medium respectively)

n2 = 1 and n1 = 1.33

d = d' x (n2/n1) = 5.3 (1/1.33) = 3.984 meters

Hence actual depth = 3.98 meters

(2)In the second problem

focal length = f = 12 cm

image distance =? and object distance =?

But its fiven that M = -i/o = 2

i = 2o

By lens formula we know that,

1/f = 1/i + 1/o

i/12 = 1/2o + 1/o = 1.5/o

which gives, o = 1.5 x 12 = 18 cm