CBSE Class 10 Science 2018 · Paper 31/1/C · Question 26(a)

Light - Reflection and Refraction 2 marks Medium

While tracing the path of a ray of light passing through a reactangular glass slab a student tabulated his observations. If in his experiment for two readings he takes two values of

∠ i

4 0^{\circ}

and

5 0^{\circ}

, what should be the correct values of

∠ e

and

∠ r

in each case ?

Answer

The angle of emergence equals the angle of incidence ( $4 0^{\circ}$ and $5 0^{\circ}$ ); for glass, $∠ r$ is about $2 5^{\circ}$ and $3 1^{\circ}$ .

∠ e = ∠ i

in each case: for

∠ i = 4 0^{\circ}

∠ e = 4 0^{\circ}

; for

∠ i = 5 0^{\circ}

∠ e = 5 0^{\circ}

(the emergent ray is parallel to the incident ray).

∠ r

must be less than

∠ i

in each case, because the ray bends towards the normal on entering glass; for ordinary glass (

n = 1.5

∠ r \approx 2 5^{\circ}

(

25. 4^{\circ}

) when

∠ i = 4 0^{\circ}

and

∠ r \approx 3 1^{\circ}

(

30. 7^{\circ}

) when

∠ i = 5 0^{\circ}

🔒 Step-by-step solution

CBSE Class 10 Science 2018 · Paper 31/1/C · Question 26(a)

Answer

From the board papers

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