SATHEE: Optics 4 Question 20

Optics 4 Question 20

21. A prism of refracting angle $30^{\circ}$ is coated with a thin film of transparent material of refractive index 2.2 on face $A C$ of the prism. A light of wavelength $6600 \AA$ is incident on face $A B$ such that angle of incidence is $60^{\circ}$ . Find

$(2003, 4$ M)

(a) the angle of emergence and

(b) the minimum value of thickness of the coated film on the face $A C$ for which the light emerging from the face has maximum intensity. (Given refractive index of the material of the prism is $\sqrt{3}$ )

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Answer:

Correct Answer: 21. (a) zero

(b) $1500 \AA$

Solution:

(a) $\sin i_{1} = μ \sin r_{1}$

$\begin{array}{lll} or & \sin 60^{\circ} = \sqrt{3} \sin r_{1} \\ ∴ & \sin r_{1} & = \frac{1}{2} or r_{1} = 30^{\circ} \\ Now, & r_{1} + r_{2} = A \\ ∴ & r_{2} & = A - r_{1} = 30^{\circ} - 30^{\circ} = 0^{\circ} \end{array}$

Therefore, ray of light falls normally on the face $A C$ and angle of emergence $i_{2} = 0^{\circ}$ .

(b) Multiple reflections occur between surface of film. Intensity will be maximum if constructive interference takes place in the transmitted wave.

For maximum thickness

$\begin{aligned} Δ x & = 2 μ t = λ (t = thickness) \\ ∴ t & = \frac{λ}{2 μ} = \frac{6600}{2 \times 2.2} = 1500 \AA \end{aligned}$

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Optics 4 Question 20

21. A prism of refracting angle $30^{\circ}$ is coated with a thin film of transparent material of refractive index 2.2 on face $A C$ of the prism. A light of wavelength $6600 \AA$ is incident on face $A B$ such that angle of incidence is $60^{\circ}$ . Find

Answer:

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Optics 4 Question 20

21. A prism of refracting angle 30∘ is coated with a thin film of transparent material of refractive index 2.2 on face AC of the prism. A light of wavelength 6600\AA is incident on face AB such that angle of incidence is 60∘. Find

Answer:

इंजीनियरिंग की तैयारी

चिकित्सा तैयारी

एनसीईआरटी पुस्तकें और समाधान

महत्वपूर्ण संसाधन

अन्य संसाधन

पाठ्यक्रम

परीक्षा मंच

नमूना मॉक टेस्ट

सदस्यता

एनसीईआरटी व्यायाम वीडियो समाधान

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21. A prism of refracting angle $30^{\circ}$ is coated with a thin film of transparent material of refractive index 2.2 on face $A C$ of the prism. A light of wavelength $6600 \AA$ is incident on face $A B$ such that angle of incidence is $60^{\circ}$ . Find