Young's Slits Questions
Q1
In a double slit interference arrangement the fringe spacing is w when the wavelength of the radiation is λ, the distance between the double slits is s and the distance between the slits and the plane of the observed fringes is D.
In which one of the following cases would the fringe spacing also be w?
|
wave length |
distance between slits |
distance between slits and fringes |
A |
2λ |
2s |
2D |
B |
2λ |
4s |
2D |
C |
2λ |
2s |
4D |
D |
4λ |
4s |
2D |
Q2.
The diagram represents the experimental arrangement used to produce interference fringes in Young's double slit experiment.
![](diagrams/yougslit.png)
The spacing of the fringes on the screen will increase if:
A |
the width of the single slit is increased |
B |
the distance XY between the two slits is increased |
C |
a light source of lower frequency is used |
D |
the distance between the single and double slits is decreased |
Q3.
Young's two slit interference pattern with red light of wavelength 7.0 × 10–7 m gives a fringe separation of 2.0 mm.
What separation, in mm, would be observed at the same place using blue light of wavelength 4.5 × 10–7 m?
Q4.
![](diagrams/yougslit2.png)
Coherent monochromatic light of wavelength λ emerges from the slits X and Y to form dark fringes at P, Q, R and S in a double slit apparatus.
Which one of the following statements is true?
A When the distance D is increased, the separation of the fringes increases.
B When the distance between X and Y is increased, the separation of the fringes increases.
C When the width of the slit T is decreased, the separation of the fringes decreases.
D There is a dark fringe at P because (YP − XP) is 2λ .
Q5.
Interference fringes, produced by monochromatic light, are viewed on a screen placed a distance D from a double slit system with slit separation s. The distance between the centres of two adjacent fringes (the fringe separation) is w. If both s and D are doubled, what will be the new fringe separation?
A w/4
B w
C 2w
D 4w
Q6.
In a Young’s double slit interference experiment, monochromatic light placed behind a single slit illuminates two narrow slits and the interference pattern is observed on a screen placed some distance away from the slits.
Which one of the following decreases the separation of the fringes?
A increasing the width of the single slit
B decreasing the separation of the double slits
C increasing the distance between the double slits and the screen
D using monochromatic light of higher frequency
Q7.
A double slit interference experiment is performed using monochromatic light of wavelength λ. The centre of the observed pattern is a bright fringe.
![](diagrams/fringes.png)
What is the path difference between two waves which interfere to give the third dark fringe from the centre?
A 0.5 λ
B 1.5 λ
C 2.5 λ
D 3.5 λ
Q8.
Interference maxima produced by a double source are observed at a distance of 1.0 m from the sources. In which one of the following cases are the maxima closest together?
A red light of wavelength 700 nm from sources 4.0 mm apart
B sound waves of wavelength 20 mm from sources 50 mm apart
C blue light of wavelength 450 nm from sources 2.0 mm apart
D surface water waves of wavelength 10 mm from sources 200 mm apart
Q9.
In a double slit system used to produce interference fringes, the separation of the slits is s and the width of each slit is x.
![](diagrams/yougslit3.png)
L is a source of monochromatic light.
Which one of the following changes would decrease the separation of the fringes seen on the screen?
A moving the screen closer to the double slits
B decreasing the width, x, of each slit, but keeping s constant
C decreasing the separation, s, of the slits
D exchanging L for a monochromatic source of longer wavelength
Q10.
Two identical loudspeakers are connected in series to an a.c. supply, as shown.
![](diagrams/Q10a.png)
Which graph best shows the variation of the intensity of the sound with distance along the line XY?
![](diagrams/Q10b.png)
![](../../../graphics/buttons/Clickhereforsolutions.png)