A lens with f = +10 cm; p = 4 cm; O = 3 cm. find the position, size, magnification, and character of the image. Light in air (n = 1.0) enters the eye (n = 1.34 for the cornea) at an angle of incidence of 30 degree with respect to the normal. What is the angle of reflection? Light in water (n = 1.33) enters the eye (n = 1.34 ) at an angle of incidence of 30 degrees with respect to the normal. What is the angle of reflection? Compare your answer and the conditions. Do you see why the images for an underwater human swimmer are so poor? Do you see why goggles which provide a layer of air next to the eye help?
Focal length f = 10 cm
Object distance p = -4 cm
Height of th eobject O = 3 cm
From the relation ( 1/q ) -( 1/p) = (1/f )
( 1/q) -(1-4) = (1/10)
(1/q)+(1/4) = (1/10)
(1/q) = (1/10) -(1/4)
= 0.1 -0.25
= -0.15
q = -6.66 cm
Position of the image is = -6.66 cm
i.e., same side as object.
We know q / p = I / O
From this height of the image I = O(q/p)
= 3 cm(-6.66 /-4)
= 5 cm
Magnification m = q / p
= 6.66/4
= 1.66
The image is virtual and erect
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