Interference (AQA A Level Physics)

The effect of a double slit on monochromatic light is observed by the set up in the diagram below.

Interference fringes are seen on the screen.

Which of the following changes would increase the distance between the adjacent fringes?

Certain situations will produce visible interference fringes from two light sources.

Which of the following conditions will enable visible interference fringes to be seen?

A student sets up an experiment that shows monochromatic light producing interference fringes. The fringes have a separation of w on a screen a distance D away from a pair of slits with separation s.

The student doubles s and D.

What would be the new fringe separation?

A double slit interference experiment is conducted using monochromatic light of wavelength . The centre of the observed pattern is a bright fringe.

What is the path difference between two waves which interfere to give the second dark fringe from the centre?

Interference maxima produced by a double source are observed a distance of 2.0 m from the sources. In which one of the following cases are the maxima furthest apart?

Two wave generators are placed at points S and R to produce sound waves with an identical wavelength. At point T both waves have the same amplitude. The distances from S to T and R to T are shown on the diagram below.

As the student walks from S to T she notices that the volume of the sound increases then decreases repeatedly.

What is the wavelength of the waves when the wave generators are coherent sources and the amplitude at T is maximum?

The diagram is a set–up of the equipment used to investigate the interference of a double slit.

Which of the following changes would increase the fringe spacing?

A student is investigating the interference of waves. They set up coherent waves produced at points S and T and travel outwards in all directions.

The line XY is halfway between S and T and perpendicular to the joining line S and T. The distance XY is much greater than the distance ST.

Which line or lines would an interference pattern be seen?

The diagram shows Young’s double slit experiment performed with a red laser as the light source.

Which option shows how the intensity varies with position for a monochromatic light source on a screen placed after the double slit?

A laser illuminates a pair of slits of separation 0.15 mm. The wavelength of light from the laser is 5.5 × 10^-7 m. Interference fringes are observed on a screen ten thousand times further away than the size of the slit separation.

What is the fringe separation as an ordinary number, not in standard form, with the appropriate SI prefix in your units?

Blue light with a wavelength of 450 nm is used in an experiment to demonstrate interference fringes produced by double-slit interference. The fringe separation is 5.0 mm and the separation of the slits is 0.70 mm.

What would be the distance between the double slit and the screen?

A Physicist carried out an experiment on Young’s slits using a laser light. The diagram below shows the equipment set up.

There is also a section of the pattern produced with a ruler placed next to it.

What is the wavelength of the light?

In a Young’s double-slit experiment, the spacing of the double slits is s and the distance between the slits and the screen on which fringes are formed is D. When monochromatic light of wavelength λ is incident on the slits the distance between adjacent fringes on the screen is w.

Which row shows another arrangement that produces a fringe spacing of w?

	Wavelength of the light	Distance between the slits and the screen	Spacing of double Slits
A		2D	4s
B		2D	2s
C		2D	2s
D		2D	8s

In the diagram, K is the source of a wave of frequency 25 Hz.

The wave travels to M by two routes, K → L → M and K → M. The speed of the wave is 15 m s^-1.

What is the path difference between the two waves at M in terms of the wavelength λ of the waves?

The diagram below shows an arrangement used to investigate double slit interference using microwaves.

The diagram below shows the view from above.

The microwaves from the transmitter are polarised. These waves are detected by the aerial in the microwave detector (probe). The aerial is a vertical metal rod.

The detector is moved along the dotted line UY. As it is moved, maximum and minimum signals are detected. Maximum signals are first detected at points V and W. The next maximum signal is detected at the position X.

The distances between each of the two slits, S₁ and S₂ and the microwave receiver when the aerial is in position X are S₁X = 0.3335 m and S₂X = 0.3615 m

 

Select the three correct reasons that explain why the signal strength falls to a minimum between U and V, and between V and W.

	Reason 1	Reason 2	Reason 3
A	Waves are out of phase	Creating the path difference	Constructive interference occurs
B	Waves are out of phase	Creating the path difference	Destructive interference occurs
C	Waves have a path difference	Path difference is a half-integer number of wavelengths	Destructive interference occurs
D	Waves have a path difference	Path difference is a half-integer number of wavelengths	Constructive interference occurs

A sound source X₁ is positioned w cm to the left of sound source X₂. Both sound sources are y m below the detection line AB. AB runs parallel to X₁X₂ . When a sound detector is slowly moved along the line AB, a maxima is first detected at P, followed by a minima at Q, with another maxima at R and a minima at S. PQRS are all equidistant apart with X₁ S = X₂ S.

 

Which one of the following is a correct expression for the wavelength of the sound?

The diagram shows the paths of microwaves from two narrow slits, acting as coherent sources, through a vacuum to a detector.

The frequency of the microwaves is 8.7 GHz.

Calculate the value of the path difference of the two waves arriving at the detector.

The screen below shows the maxima of a two slit interference pattern produced on a screen when a laser was used as a monochromatic light source.

The slit spacing is 0.45 mm.

The distance from the slits to the screen = 9.6 m.

Use the diagram above to calculate the wavelength of the light that produced the pattern.

White light is passed through a double slit and an interference pattern is observed on a screen 2.1 m away. The separation between the slits is 0.6 mm. The first violet and red fringes are formed 1.8 mm and 3.3 mm respectively away from the central white fringe.

What are the wavelengths of the violet and red light?

Green light with a wavelength of 550 nm is used in an experiment to show interference fringes produced by double-slit interference. The fringe separation is 3.5 mm and the separation of the slits is 0.70 mm.

What would be the distance between the double slit and the screen?