The human eye is not able to see an object distinctly if it subtends an angle :

1. equal to 10'
2. less than 1'
3. more than 1'
4. more than 5'

A simple microscope uses a :

1. convex lens of short focal length
2. convex lens of large focal length
3. concave lens of short focal length
4. concave lens of large focal length

A person suffering from long sightedness wears spectacles having a …………… lens and a person suffering from short sightedness wears spectacles having …………… lens.

1. convex, convex
2. concave, concave
3. concave, convex
4. convex, concave

A boy has two lenses A and B. When lens A is kept near a printed page, letters appear magnified. When lens B is used to see a distant object, an upright image is seen. The lenses A and B are :

1. both are convex
2. both are concave
3. A ⟶ concave, B ⟶ convex
4. A ⟶ convex, B ⟶ concave