Quiz on Chapter 28

Question 1

In Young’s two-slit experiment, the first dark fringe above the central bright fringe occurs at an angle of 0.31 degrees. What is the ratio of the slit separatiory d, to the wavelength of the light?

Answer 1

L2 - L1= (m-.5) lambda

we know L= d sin(theta)

d sin(theta)= (m-0.5) lambda

Question 2

Light from a He-Ne laser ( wavelength= 632.8 nm) strikes a pair of slits at normal incidence, forming a double-slit interference pattern on a screen located 1.4m from the slits shows the interference pattern observed on the screen. What is the slit separation?

Answer 2

Question 3

A soap bubble with walls 401 nm thick floats in air. If this bubble is illuminated perpendicularly with sunlight, what wavelength (and color) will be absent in the reflected light? Assume that the index of refraction of the soap film is 1.33. (Refer to Example 25-3 for the connection between-wavelength and color.)

Answer 3

t= 401nm

n= 1.33

For a vacuum: m= 2nt/ (lambda vacuum)

Question 4

A thin layer of magnesium fluoride (n= 1.38) is used to coat a flint-glass lens (n= 1.61). (a) What thickness should the magnesium fluoride film have if the reflection of 565-nm light is to be suppressed? Assume that the light is incident at right angles to the film. (b) If it is desired to suppress the reflection of light with a higher frequency, should the coating of magnesium fluoride be made thinner or thicker? Explain.

Answer 4

Non reflective coating: 2t/ lambda = 0.5

t= lambda/4

Question 5

White light is incident normally on a thin soap film (n : 1.33) suspended in air. (a) What are the two minimum thicknesses that will constructively reflect yellow (Lamda= 590 nm) light? (b) What are the two minimum thicknesses that wili destructively reflect yellow (Lamda: 590 nm) light?

Answer 5

Question 6

A grating has 787 lines per centimeter. Find the angles of the first three principal maxima above the central fringe when this grating is illuminated with 655-nm light.

Answer 6

Question 7

The diffraction pattern shown in the figure is produced by passing He-Ne laser light (Lamda= 632.8nm) through a single slit and viewing the pattern on a screen 1.50 m behind the slit. (a) What is the width of the slit? (b) If monochromatic vellow ligit with a wavelength of 591 nm is used with this slit instead, will the distance indicated in the figure be greater than or less than 15.2 cm? Explain.

Answer 7

Question 8

What is the equation for the path difference in Young’s two slit experiment?

Answer 8

Change of l = d sin(theta)

Where lambda = d sin(theta)

sin(theta) = lambda/d