In Young’s double-slit experiment, an interference pattern is obtained on a screen by a light of wavelength 6000 Å, coming from the coherent sources S1 and S2. At certain point P on the screen third dark fringe is formed. Then the path difference S1PS2P in microns is

(1) 0.75

(2) 1.5

(3) 3.0

(4) 4.5

Concept Questions :-

Young Double slit experiment
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In Young’s double-slit experiment the fringe width is β. If entire arrangement is placed in a liquid of refractive index n, the fringe width becomes

(1) $\frac{\beta }{n+1}$

(2)

(3) $\frac{\beta }{n}$

(4) $\frac{\beta }{n-1}$

Concept Questions :-

Young Double slit experiment
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In Young’s double slit experiment, distance between two sources is 0.1 mm. The distance of screen from the sources is 20 cm. Wavelength of light used is 5460 Å. Then angular position of the first dark fringe is

(1) 0.08°

(2) 0.16°

(3) 0.20°

(4) 0.313°

Concept Questions :-

Young Double slit experiment
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In a Young’s double slit experiment, the slit separation is 0.2 cm, the distance between the screen and slit is 1m. Wavelength of the light used is 5000 Å. The distance between two consecutive dark fringes (in mm) is

(1) 0.25

(2) 0.26

(3) 0.27

(4) 0.28

Concept Questions :-

Young Double slit experiment
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A star emitting light of wavelength 5896 Å is moving away from the earth with a speed of 3600 km/sec. The wavelength of light observed on earth will

(1) Decrease by 5825.25 Å

(2) Increase by 5966.75 Å

(3) Decrease by 70.75 Å

(4) Increase by 70.75 Å

(c = 3 × 108 m/sec is the speed of light)

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A heavenly body is receding away from the earth such that the fractional change in λ is 1, then its velocity is :

(1) C

(2) $\frac{3C}{5}$

(3) $\frac{C}{5}$

(4) $\frac{2C}{5}$

Concept Questions :-

Wave front
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A slit of width a is illuminated by white light. For red light (λ = 6500 Å), the first minima is obtained at θ = 30°. Then the value of a will be

(1) 3250 Å

(2) 6.5 × 10–4 mm

(3) 1.24 microns

(4) 2.6 × 10–4 cm

Concept Questions :-

Diffraction
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The radius of central zone of the circular zone plate is 2.3 mm. The wavelength of incident light is $5893\text{\hspace{0.17em}\hspace{0.17em}}Å.$ Source is at a distance of 6m. Then the distance of the first image will be

(1) 9 m

(2) 12 m

(3) 24 m

(4) 36 m

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Huygens' principle
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What will be the angular width of central maxima in Fraunhoffer diffraction when light of wavelength $6000\text{\hspace{0.17em}}Å$ is used and slit width is 12×10–5 cm

Concept Questions :-

Diffraction
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Direction of the first secondary maximum in the Fraunhofer diffraction pattern at a single slit is given by (a is the width of the slit)

(1) $a\mathrm{sin}\theta =\frac{\lambda }{2}$

(2) $a\mathrm{cos}\theta =\frac{3\lambda }{2}$

(3) $a\mathrm{sin}\theta =\lambda$

(4) $a\mathrm{sin}\theta =\frac{3\lambda }{2}$

Concept Questions :-

Diffraction