physics(blooming of lens)

Question

AL phy paperII MC Q15

A coating material of refractive index 1.25 is used for the blooming of a lens having a larger refractive index. For narmal incidence, if green light is to be transmitted in its greatest amount through the lens, which of the following thicknesses of the coating would do?

(Given: wavelength of green light in air is 550nm)

(1) 137.5nm

(2) 220nm

(3) 330nm

A. (1) only

B. (3) only

C. (1) and (2) only

D. (2) and (3) only

E. (1), (2) and (3)

Answer 1

最愛解答

By blooming of lens,

2nd = (m - 1/2)入, for m is a positive integer

d = (m - 1/2)入/2n

Thickness of the lens, d = (m - 1/2)(550 X 10^-9)/2(1.25) = 2.2 X 10^-7(m - 1/2)

Put m = 1, d = 1.1 X 10^-7 m

Put m = 2, d = 3.3 X 10^-7 m

And put m = 3 or more, the value of d is larger than the three options.

So, The answer is B. (3) only

資料來源： Physics king