Question

If the refractive index of the lens material is less than that of the surrounding liquid (\[n_2 < n_1\]), then:

Options

• the lens becomes invisible

• the power of the lens remains unchanged

• the lens keeps its nature, but its power decreases

• the lens changes its nature (convex behaves like concave and vice versa)

Answer 1

When \[n_2 < n_1\], the refractive-index difference reverses in sign, so the lens changes its nature: a convex lens behaves like a concave lens and vice versa.