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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Difficulty Level:

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

Concept Questions :-

Huygens' principle
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Difficulty Level:

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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Difficulty Level:

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
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Difficulty Level:

A parallel monochromatic beam of light is incident normally on a narrow slit. A diffraction pattern is formed on a screen placed perpendicular to the direction of the incident beam. At the first maximum of the diffraction pattern, the phase difference between the rays coming from the edges of the slit is

(1) $0$

(2) $\frac{\pi }{2}$

(3) $\pi$

(4) 2$\pi$

Concept Questions :-

Diffraction
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Difficulty Level:

A parallel beam of monochromatic light of wavelength 5000 Å is incident normally on a single narrow slit of width 0.001 mm. The light is focused by a convex lens on a screen placed on the focal plane. The first minimum will be formed for the angle of diffraction equal to

(1) 0o

(2) 15o

(3) 30o

(4) 60o

Concept Questions :-

Diffraction
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Difficulty Level:

In the far field diffraction pattern of a single slit under polychromatic illumination, the first minimum with the wavelength ${\lambda }_{1}$ is found to be coincident with the third maximum at ${\lambda }_{2}$. So

(1) $3{\lambda }_{1}=0.3{\lambda }_{2}$

(2) $3{\lambda }_{1}={\lambda }_{2}$

(3) ${\lambda }_{1}=3.5{\lambda }_{2}$

(4) $0.3{\lambda }_{1}=3{\lambda }_{2}$

Concept Questions :-

Diffraction
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Difficulty Level:

The angle of polarisation for any medium is 60o, what will be critical angle for this

(1) ${\mathrm{sin}}^{-1}\sqrt{3}$

(2) ${\mathrm{tan}}^{-1}\sqrt{3}$

(3) ${\mathrm{cos}}^{-1}\sqrt{3}$

(4) ${\mathrm{sin}}^{-1}\frac{1}{\sqrt{3}}$

Concept Questions :-

Polarization of light
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Difficulty Level:

A beam of light AO is incident on a glass slab (μ = 1.54) in a direction as shown in figure. The reflected ray OB is passed through a Nicol prism on viewing through a Nicole prism, we find on rotating the prism that

(1) The intensity is reduced down to zero and remains zero

(2) The intensity reduces down some what and rises again

(3) There is no change in intensity

(4) The intensity gradually reduces to zero and then again increases

Concept Questions :-

Polarization of light
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Difficulty Level:

In the propagation of electromagnetic waves, the angle between the direction of propagation and plane of polarisation is

(1) 0o

(2) 45o

(3) 90o

(4) 180o

Concept Questions :-

Polarization of light