MHT CET · Physics · Ray Optics

A ray of light is incident normally on a glass slab of thickness $5 cm$ and refractive index $1.6$ . The time taken to travel by a ray from source to surface of the slab is the same as to travel through glass slab. The distance of the source from the surface is

A $4 cm$
B $8 cm$
C $12 cm$
D $16 cm$

Verified Solution

Answer & Solution

Correct Answer

(B) $8 cm$

Step-by-step Solution

Detailed explanation

Velocity of light in medium,

v = \frac{5}{t}

Velocity of light in vaccum,

c = \frac{x}{t}

μ = \frac{c}{v} = \frac{x}{5}

x = 5 μ = 8 cm

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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A ray of light is incident normally on a glass slab of thickness 5 cm and refractive index 1.6. The time taken to travel by a ray from source to surface of the slab is the same as to travel through glass slab. The distance of the source from the surface is

Step-by-step Solution

A ray of light is incident normally on a glass slab of thickness $5 cm$ and refractive index $1.6$ . The time taken to travel by a ray from source to surface of the slab is the same as to travel through glass slab. The distance of the source from the surface is