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ABC is a glass block whose two sides, AB and BC, are at right angles to each other. A ray of light is incident on the surface AB, as shown in the diagram, and suffers total internal reflection before falling on the surface BC. Finally, the light ray emerges out along the surface BC.

ABC is a glass block whose two sides, AB and BC, are at right angles to each other. A ray of light is incident on the surface AB, as shown in the diagram, and suffers total internal reflection before falling on the surface BC. Finally, the light ray emerges out along the surface BC. Physics Competency Focused Practice Questions Class 10 Solutions.

(a) What is the angle of incidence at the surface AB?

(b) What is the critical angle for the glass block BC?

(c) What would happen to the critical angle if the temperature of the glass block is increased?

Refraction Plane Surfaces

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Answer

ABC is a glass block whose two sides, AB and BC, are at right angles to each other. A ray of light is incident on the surface AB, as shown in the diagram, and suffers total internal reflection before falling on the surface BC. Finally, the light ray emerges out along the surface BC. Physics Competency Focused Practice Questions Class 10 Solutions.

(a)

∠r = ∠NQR = ∠QRB (alternate angle)

∠QRC + ∠QRB = 180°

∠QRB = 180° - ∠QRC

∠r = 180° − 132° = 48°

∠i = ∠r [∵ Law of reflection]

∴ ∠i = 48°

(b) ∠ic = ∠QRN' = 132° − 90° = 42°

(c) On increasing the temperature of a medium, its refractive index decreases, therefore the critical angle increases with the increase in temperature.

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