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Worksheet: Thin Lenses


A camera with a 100 mm-focal length lens is used to photograph the Sun. What is the height of the Sun’s image at the camera’s photosensor? Use a value of km for the diameter of the Sun and use a value of km for the distance to the Sun.


A slide projector uses a mm-focal length lens to project images onto a screen.

How far away is the screen if a slide is placed 103 mm from the lens and produces a sharp image on the screen?

If the dimensions of the slide are 24.0 cm by 36.0 mm, what are the dimensions of the image on the screen?

  • A
  • B
  • C
  • D
  • E


Suppose your 50.0 mm-focal length camera lens is 51.0 mm away from the film in the camera.

How far away is an object that is in focus?

What is the height of the object if its image is 2.00 cm high?


A 10.0 cm-focal length lens produces a magnification of for a book held 7.50 cm from it.

Find the magnification for the book when it is held 8.50 cm from the magnifier.

Find the magnification for the book when it is held 9.50 cm from the magnifier.


A camera with a 50.0-mm focal length lens is being used to photograph a person standing 3.00 m away.

How far from the camera’s lens is its photosensor?

What is the maximum height of a person whose image can be formed onto a 36.0 mm high section of photosensor using this camera at this distance?


A lens of focal length 20 cm is placed 10 cm in front of a second identical lens. A concave mirror of focal length 15 cm is placed 50 cm behind the second lens. An object of height 3.0 cm is placed 25 cm in front of the first lens.

Find the distance in front of the mirror of the final image formed.

Find the size of the final image formed.


An object has a height of 3.0 cm. The object is placed 5.0 cm in front of a converging lens of focal length 20 cm. An observer sees an image of the object formed on the opposite side of the lens to where the object is located.

How far from the lens is the image?

What is the height of the image?


A lens has a focal length of 20 cm. Parallel light rays from a distant source strike the lens at an angle of from its optical axis. Find the distance from the axis of the real image observed on a screen in the focal plane of the lens.


Find the focal length of a thin plano-convex lens. The front surface of this lens is flat, and the rear surface has a radius of curvature of cm. The refractive index of the lens is 1.5.