Correct Answer - Option 3 : 30°
CONCEPT:
Diffraction of Light:
- The phenomenon of bending of waves around the corners of an obstacle/aperture of the size of the wavelength of a wave is called diffraction.
- Diffraction is the characteristic of all types of waves.
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The greater the wavelength of the wave higher will be its degree of diffraction.
- The condition of diffraction is that the width of the obstacle must be less than or comparable with the wavelength of the wave.
Types of diffraction:
- Fresnel diffraction
- Fraunhofer diffraction
Fraunhofer diffraction:
- In this type of diffraction, both source and screen are effectively at an infinite distance from the diffracting surface.
- In Fraunhofer diffraction, the plane wavefront is incident on the slit.
- In Fraunhofer diffraction, the diffraction pattern consists of a central bright fringe surrounded by dark and bright lines.
- The angle of diffraction for the nth minima is given as,
\(⇒ sin\theta=\frac{nλ}{b}\)
Where λ = wavelength and b = width of the slit
EXPLANATION:
Given n = 1, λ = 5000 Å =5000×10-10 m and b = 0.001 mm = 0.0010×10-3 m
- We know that the angle of diffraction for the nth minima is given as,
\(⇒ sin\theta=\frac{nλ}{b}\)
\(⇒ sin \theta =\frac{1\times5000× 10^{-10}}{.001× 10^{-3}}\)
\(⇒ sin \theta =\frac{1}{2}\)
⇒ θ = 30º
- Hence, option 3 is correct.