An image of small size can be obtained on a screen placed at 2.0 m from object. It can be done by using:

(A) concave mirror of focal length 0.5 m
(B) concave mirror of focal length greater than 0.5 m
(C) concave mirror of focal length less than 0.5 m
(D) concave lens of focal length less than 0.5 m.

Can you provide a good solution for this? Thank you

Note by Sahba Hasan
5 years, 9 months ago

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- 5 years, 9 months ago

B will be the option as in that case, the object will be placed between centre of curvature and focal length. Since the object is placed at 2 m away from the mirror, and it has to be in between Curvature and focus. The centre of curvature therefore should be greater than 2 m which makes focal length automatically greater than 0.5 m.

- 5 years, 9 months ago

You got it wrong @Abhay Tiwari ...The object distance is not given, the distance of the image from the object is given.

- 5 years, 9 months ago

Still the answer remains B :p

- 5 years, 9 months ago

I can't understand how...@Abhay Tiwari ...

- 5 years, 9 months ago

What have you tried? What do you know?

Staff - 5 years, 9 months ago

I know that option D is not true because a concave lens won't produce an image which can be obtained on a screen, i.e it won't produce a real image. The things which i can't figure out are the three options left. In the question the object distance is not given. 2.0 m is mere distance of screen from the object, i.e. image from the object.

How can i figure out the focal length of the mirror?

- 5 years, 9 months ago