EASY
AS and A Level
IMPORTANT
Earn 100

A student is trying to make an accurate measurement of the wavelength of green light from a mercury lamp. The wavelength $\lambda$ of this light is 546 nm. Using a double-slit of separation 0.50 mm, the student can see 10 clear bright fringes on a screen at a distance of 0.80 m from the slits. The student can measure their overall width to within ±1 mm

Using a ruler. The student then tries an alternative experiment using a diffraction grating with 3000 lines cm-1. The angle between the two second-order maxima can be measured to within ±0.1°.

(a) Determine the width of the 10 fringes that the student can measure in the first experiment.

Important Questions on Superposition of Waves

EASY
AS and A Level
IMPORTANT

A student is trying to make an accurate measurement of the wavelength of green light from a mercury lamp. The wavelength $\lambda$ of this light is 546 nm. Using a double-slit of separation 0.50 mm, the student can see 10 clear bright fringes on a screen at a distance of 0.80 m from the slits. The student can measure their overall width to within ±1 mm

Using a ruler. The student then tries an alternative experiment using a diffraction grating with 3000 lines cm-1. The angle between the two second-order maxima can be measured to within ±0.1°.

(b) Determine the angle of the second-order maximum that the student can measure in the second experiment.

EASY
AS and A Level
IMPORTANT

A student is trying to make an accurate measurement of the wavelength of green light from a mercury lamp. The wavelength $\lambda$ of this light is 546 nm. Using a double-slit of separation 0.50 mm, the student can see 10 clear bright fringes on a screen at a distance of 0.80 m from the slits. The student can measure their overall width to within ±1 mm

Using a ruler. The student then tries an alternative experiment using a diffraction grating with 3000 lines cm-1. The angle between the two second-order maxima can be measured to within ±0.1°.

(c) Based on your answers to parts a and b, suggest which experiment you think will give the more accurate value of λ.

MEDIUM
AS and A Level
IMPORTANT

White light is incident normally on a diffraction grating with a slit-separation d of 2.00×10-6 m. The visible spectrum has wavelengths between 400 nm and 700 nm.

(a) Calculate the angle between the red and violet ends of the first-order spectrum.

EASY
AS and A Level
IMPORTANT

White light is incident normally on a diffraction grating with a slit-separation d of 2.00×10-6 m. The visible spectrum has wavelengths between 400 nm and 700 nm.

(b) Explain why the second-and third-order spectra overlap.

EASY
AS and A Level
IMPORTANT
Make a short list of everyday items that would diffract sound, then do the same for light.
EASY
AS and A Level
IMPORTANT
Summarise two experiments for your fellow learners for determining the wavelength of visible light. What did you learn about yourself as you worked on this summary?
EASY
AS and A Level
IMPORTANT

Rays of light from two coherent sources produces constructive interference. Which of the following cannot be the phase difference between these two rays?

(A) 0°

(B) 270°

(C) 360°

(D) 720°

EASY
AS and A Level
IMPORTANT

(a) Copy the waves shown in the diagram onto a sheet of graph paper and use the principle of superposition to sketch the resultant wave.

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