Question

For finding the focal length of a convex lens by obtaining the image of a distant object, one should use as the object. (1) a well lit distant tree (2) window grill in the class room (3) any distant tree (4) a lighted candle kept at the other end of the table.

Answer 1

Answer is option 4)

A lighted candle kept at the other end of the table

Answer 2

Answer:

A well-lit distant tree should be the object. Option (1) is correct.

Explanation:

• We use a convex lens to converge a beam of light at a particular point.
• For the magnification purpose, we use a convex lens.
• When we place an object at infinity, the image is obtained at the focus.

The object that is placed at infinity should be bright and well lit. This requirement is must as an accurate, bright, and sharp image should be there at the focus to calculate the focal length.

So, a well-lit distant tree should be the object.

Option (1) is correct.