Question 1

The widths of the lines produced by monochromatic light falling on a diffraction grating can be reduced by:

Accepted Answer

A)  increasing the wavelength of the light 
B)  increasing the number of rulings without changing their spacing 
C)  decreasing the spacing between adjacent rulings without changing the number of rulings 
D)  decreasing both the wavelength and the spacing between rulings by the same factor 
E)  increasing the number of rulings and decreasing their spacing so the length of the grating remains the same 
A)  increasing the wavelength of the light 
B)  increasing the number of rulings without changing their spacing 
C)  decreasing the spacing between adjacent rulings without changing the number of rulings 
D)  decreasing both the wavelength and the spacing between rulings by the same factor 
E)  increasing the number of rulings and decreasing their spacing so the length of the grating remains the same B

Question 2

A diffraction grating just resolves the wavelengths 400.0 nm and 400.1 nm in first order. The number of slits in the grating is:

Accepted Answer

A)  400 
B)  1000 
C)  2500 
D)  4000 
E)  not enough information is given 
A)  400 
B)  1000 
C)  2500 
D)  4000 
E)  not enough information is given D

Question 3

No fringes are seen in a single-slit diffraction pattern if:

Accepted Answer

A)  the screen is far away 
B)  the wavelength is less than the slit width 
C)  the wavelength is greater than the slit width 
D)  the wavelength is less than the distance to the screen 
E)  the distance to the screen is greater than the slit width 
A)  the screen is far away 
B)  the wavelength is less than the slit width 
C)  the wavelength is greater than the slit width 
D)  the wavelength is less than the distance to the screen 
E)  the distance to the screen is greater than the slit width C

Question 4

Sound differs from light in that sound:

Accepted Answer

A)  is not subject to diffraction 
B)  is a torsional wave rather than a longitudinal wave 
C)  does not require energy for its origin 
D)  is a longitudinal wave rather than a transverse wave 
E)  is always monochromatic 
A)  is not subject to diffraction 
B)  is a torsional wave rather than a longitudinal wave 
C)  does not require energy for its origin 
D)  is a longitudinal wave rather than a transverse wave 
E)  is always monochromatic

Question 5

Light of wavelength$\lambda$ is normally incident on a diffraction grating G. On the screen S, the central line is at P and the first order line is at Q, as shown. The distance between adjacent slits in the grating is:

Accepted Answer

A)  3$\lambda$/5 
B)  3$\lambda$/4 
C)  4$\lambda$/5 
D)  5$\lambda$/4 
E)  5$\lambda$/3 
A)  3$\lambda$/5 
B)  3$\lambda$/4 
C)  4$\lambda$/5 
D)  5$\lambda$/4 
E)  5$\lambda$/3

Question 6

An x-ray beam of wavelength 3 *10-11 m is incident on a calcite crystal of lattice spacing 0.3 nm. The smallest angle between crystal planes and the x-ray beam which will result in constructive interference is:

Accepted Answer

A)  2.9° 
B)  5.7° 
C)  12° 
D)  23° 
E)  none of these 
A)  2.9° 
B)  5.7° 
C)  12° 
D)  23° 
E)  none of these

Question 7

If we increase the wavelength of the light used to form a double-slit diffraction pattern:

Accepted Answer

A)  the width of the central diffraction peak increases and the number of bright fringes within the peak increases 
B)  the width of the central diffraction peak increases and the number of bright fringes within the peak decreases 
C)  the width of the central diffraction peak decreases and the number of bright fringes within the peak increases 
D)  the width of the central diffraction peak decreases and the number of bright fringes within the peak decreases 
E)  the width of the central diffraction peak increases and the number of bright fringes within the peak stays the same 
A)  the width of the central diffraction peak increases and the number of bright fringes within the peak increases 
B)  the width of the central diffraction peak increases and the number of bright fringes within the peak decreases 
C)  the width of the central diffraction peak decreases and the number of bright fringes within the peak increases 
D)  the width of the central diffraction peak decreases and the number of bright fringes within the peak decreases 
E)  the width of the central diffraction peak increases and the number of bright fringes within the peak stays the same

Question 8

A plane wave with a wavelength of 500 nm is incident normally on a single slit with a width of 5.0*10-6 m. Consider waves that reach a point on a far-away screen such that rays from the slit make an angle of 1.0  $\degree$with the normal. The difference in phase for waves from the top and bottom of the slit is:

Accepted Answer

A)  0 rad 
B)  0.55 rad 
C)  1.1 rad 
D)  1.6 rad 
E)  2.2 rad 
A)  0 rad 
B)  0.55 rad 
C)  1.1 rad 
D)  1.6 rad 
E)  2.2 rad

Question 9

The resolving power R of a grating can have units:

Accepted Answer

A)  cm 
B)  degree/nm 
C)  watt 
D)  nm/cm 
E)  watt/nm 
A)  cm 
B)  degree/nm 
C)  watt 
D)  nm/cm 
E)  watt/nm

Question 10

In a single-slit diffraction pattern, the central maximum is about twice as wide as the other maxima. This is because:

Accepted Answer

A)  half the light is diffracted up and half is diffracted down 
B)  the central maximum has both electric and magnetic fields present 
C)  the small angle approximation applies only near the central maximum 
D)  the screen is flat instead of spherical 
E)  none of the above 
A)  half the light is diffracted up and half is diffracted down 
B)  the central maximum has both electric and magnetic fields present 
C)  the small angle approximation applies only near the central maximum 
D)  the screen is flat instead of spherical 
E)  none of the above

Question 11

Two wavelengths, 800 nm and 600 nm, are used separately in single-slit diffraction experiments. The diagram shows the intensities on a far-away viewing screen as function of the angle made by the rays with the straight-ahead direction. If both wavelengths are then used simultaneously, which point corresponds to the smallest angle at which the light on the screen is purely 800-nm light?

Accepted Answer

A)  A 
B)  B 
C)  C 
D)  D 
E)  E 
A)  A 
B)  B 
C)  C 
D)  D 
E)  E

Question 12

The intensity of the single-slit diffraction pattern at any angle θ is given by . For light of wavelength 480 nm falling on a slit of width 3.5 µm, what is the value of α when θ = 18°?

Accepted Answer

A)  0.31 rad 
B)  2.3 rad 
C)  7.1 rad 
D)  7.3 rad 
E)  9.8 rad 
A)  0.31 rad 
B)  2.3 rad 
C)  7.1 rad 
D)  7.3 rad 
E)  9.8 rad

Question 13

X rays are:

Accepted Answer

A)  electromagnetic waves 
B)  negatively charged ions 
C)  rapidly moving electrons 
D)  rapidly moving protons 
E)  rapidly moving neutrons 
A)  electromagnetic waves 
B)  negatively charged ions 
C)  rapidly moving electrons 
D)  rapidly moving protons 
E)  rapidly moving neutrons

Question 14

What is the minimum number of slits required in a diffraction grating to just resolve light with wavelengths of 471.0 nm and 471.6 nm?

Accepted Answer

A)  99 
B)  197 
C)  393 
D)  786 
E)  1179 
A)  99 
B)  197 
C)  393 
D)  786 
E)  1179

Question 15

A light spectrum is formed on a screen using a diffraction grating. The entire apparatus (source, grating and screen) is now immersed in a liquid of index 1.33. As a result, the pattern on the screen:

Accepted Answer

A)  remains the same 
B)  spreads out 
C)  crowds together 
D)  becomes reversed, with the previously blue end becoming red 
E)  disappears because the index isn't an integer 
A)  remains the same 
B)  spreads out 
C)  crowds together 
D)  becomes reversed, with the previously blue end becoming red 
E)  disappears because the index isn't an integer

Question 16

Consider a single-slit diffraction pattern caused by a slit of width a. There is a minimum at sin$\theta$equal to:

Accepted Answer

A)  exactly $\lambda$/a 
B)  slightly more than $\lambda$/a 
C)  slightly less than $\lambda$/a 
D)  exactly $\lambda$/2a 
E)  very nearly $\lambda$/2a 
A)  exactly $\lambda$/a 
B)  slightly more than $\lambda$/a 
C)  slightly less than $\lambda$/a 
D)  exactly $\lambda$/2a 
E)  very nearly $\lambda$/2a

Question 17

A parallel beam of monochromatic light is incident on a slit of width 2 cm. The light passing through the slit falls on a screen 2 m away. As the slit width is decreased:

Accepted Answer

A)  the width of the pattern on the screen continuously decreases 
B)  the width of the pattern on the screen at first decreases but then increases 
C)  the width of the pattern on the screen increases and then decreases 
D)  the width of the pattern on the screen remains the same 
E)  the width of the pattern on the screen continuously increases 
A)  the width of the pattern on the screen continuously decreases 
B)  the width of the pattern on the screen at first decreases but then increases 
C)  the width of the pattern on the screen increases and then decreases 
D)  the width of the pattern on the screen remains the same 
E)  the width of the pattern on the screen continuously increases

Question 18

Light of wavelength 550 nm is incident on a diffraction grating that is 1 cm wide and has 1000 slits. What is the half-width of the m = 1 line?

Accepted Answer

A)  5.5 x 10-5 rad 
B)  5.5 x 10-4 rad 
C)  5.5 x 10-3 rad 
D)  5.5 x 10-2 rad 
E)  5.5 x 10-1 rad 
A)  5.5 x 10-5 rad 
B)  5.5 x 10-4 rad 
C)  5.5 x 10-3 rad 
D)  5.5 x 10-2 rad 
E)  5.5 x 10-1 rad

Question 19

A beam of x-rays of wavelength 0.20 nm is diffracted by a set of planes in a crystal whose separation is 3.1 *10-8 cm. The smallest angle between the beam and the crystal planes for which a reflection occurs is:

Accepted Answer

A)  0.70 rad 
B)  0.33 rad 
C)  0.066 rad 
D)  0.033 rad 
E)  0.0033 rad 
A)  0.70 rad 
B)  0.33 rad 
C)  0.066 rad 
D)  0.033 rad 
E)  0.0033 rad

Question 20

If white light is incident on a diffraction grating:

Accepted Answer

A)  the first order lines for all visible wavelengths occur at smaller diffraction angles than any of the second order lines 
B)  some first order lines overlap the second order lines if the ruling separation is small but do not if it is large 
C)  some first order lines overlap second order lines if the ruling separation is large but do not if it is small 
D)  some first order lines overlap second order lines no matter what the ruling separation 
E)  first and second order lines have the same range of diffraction angles 
A)  the first order lines for all visible wavelengths occur at smaller diffraction angles than any of the second order lines 
B)  some first order lines overlap the second order lines if the ruling separation is small but do not if it is large 
C)  some first order lines overlap second order lines if the ruling separation is large but do not if it is small 
D)  some first order lines overlap second order lines no matter what the ruling separation 
E)  first and second order lines have the same range of diffraction angles

Exam 36: Diffraction

The widths of the lines produced by monochromatic light falling on a diffraction grating can be reduced by:

A diffraction grating just resolves the wavelengths 400.0 nm and 400.1 nm in first order. The number of slits in the grating is:

No fringes are seen in a single-slit diffraction pattern if:

Sound differs from light in that sound:

Light of wavelength λ\lambdaλ is normally incident on a diffraction grating G. On the screen S, the central line is at P and the first order line is at Q, as shown. The distance between adjacent slits in the grating is:

An x-ray beam of wavelength 3 *10-11 m is incident on a calcite crystal of lattice spacing 0.3 nm. The smallest angle between crystal planes and the x-ray beam which will result in constructive interference is:

If we increase the wavelength of the light used to form a double-slit diffraction pattern:

The resolving power R of a grating can have units:

In a single-slit diffraction pattern, the central maximum is about twice as wide as the other maxima. This is because:

The intensity of the single-slit diffraction pattern at any angle θ is given by . For light of wavelength 480 nm falling on a slit of width 3.5 µm, what is the value of α when θ = 18°?

X rays are:

What is the minimum number of slits required in a diffraction grating to just resolve light with wavelengths of 471.0 nm and 471.6 nm?

A light spectrum is formed on a screen using a diffraction grating. The entire apparatus (source, grating and screen) is now immersed in a liquid of index 1.33. As a result, the pattern on the screen:

Consider a single-slit diffraction pattern caused by a slit of width a. There is a minimum at sin θ\thetaθ equal to:

A parallel beam of monochromatic light is incident on a slit of width 2 cm. The light passing through the slit falls on a screen 2 m away. As the slit width is decreased:

Light of wavelength 550 nm is incident on a diffraction grating that is 1 cm wide and has 1000 slits. What is the half-width of the m = 1 line?

A beam of x-rays of wavelength 0.20 nm is diffracted by a set of planes in a crystal whose separation is 3.1 *10-8 cm. The smallest angle between the beam and the crystal planes for which a reflection occurs is:

If white light is incident on a diffraction grating:

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An x-ray beam of wavelength 3 *10^-11 m is incident on a calcite crystal of lattice spacing 0.3 nm. The smallest angle between crystal planes and the x-ray beam which will result in constructive interference is:

Consider a single-slit diffraction pattern caused by a slit of width a. There is a minimum at sin $\theta$ equal to:

A beam of x-rays of wavelength 0.20 nm is diffracted by a set of planes in a crystal whose separation is 3.1 *10^-8 cm. The smallest angle between the beam and the crystal planes for which a reflection occurs is: