Explanation
The atmospheric refraction is responsible for twinkling of stars. As the light from the stars enters the earth’s atmosphere it suffers refraction and cause the twinkling.
Given that,
Power P1=40D
Power P2=20D
Total power of the combination
P=P1+P2
P=40+20
P=60D
Now, focal length of the combination
f=160×100
f=53cm
Now, for minimum converging state of the eye lens object is at infinity
u=−∞
f=53
Now, from lens equation
1f=1v−1u
35=1v−1∞
1v=35
v=53cm
So, the distance between retina and cornea – lens system 1.67 cm
The eye lens is an elastic muscular lens that controls the formation of an image on the retina. It is connected by ciliary muscles which control the shape of the eye lens. When the light coming from a far object the lens got stretched by ciliary muscles results in a decrease in the thickness of the lens and when light coming from nearby objects the thickness of the lens increases.
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