A converging lens is made of a type of glass (n_glass = 1.6). The glass is place

Question

A converging lens is made of a type of glass (n_glass = 1.6). The glass is placed in air (n=1) and the rays converge at the focal point, as shown below. When the lens is placed in water (n_water = 1.33) instead, where will the rays converge? Specifically - at the same point, at a further distance from the lens, or a shorter distance from the lens? We're learn more about the eye soon; this fact means that your eye, which basically is a converging lens that acts like a camera, doesn't focus well when under water. Multiple choice questions: You set up a lens and screen to make an image of a distant light. The light begins moving towards the lens. What must you do to keep the image sharp? Check all that apply. Move the screen towards the lens Move the screen away from the lens Use a lens with a different focal length (power) When the lens is closest to the film you are focused on an object that is nearby far away Which is true of a telephoto lens, which allows you to see a larger image of a small far away object? It has a long focal length and results in a bright image It has a long focal length and results in a dim image It has a short focal length and results in a bright image It has a short focal length and results in a dim image

Explanation / Answer

3)
let R1 and R2 are the radii of curvatures of the lens.

in the air,

1/f = (n_glass - 1)*(1/R1 - 1/R2)

in the water,

1/f' = (n_glass/n_water - 1)*(1/R1 - 1/R2)

from the above two equations,

f'/f = (n_glass - 1)/(n_glass/n_water - 1)

= (1.6 - 1)/(1.6/1.33 - 1)

= 2.95

f' = 2.95*f

so, the rays will converge at a further distance from the lens.

4)

MC1) B) move the screen away from the lens.

MC2) b) far away

MC3) b)

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