Deviation of Prism in Water – Rankers Physics

Refraction by Prism: Practice Problem & Solution

Assertion (A): When a glass prism is immersed in water, the deviation caused by prism decrease. Reason (R): Refractive index of glass prism relative to water is less than relative to air.  
Both (A) & (R) are true and the (R) is the correct explanation of the (A)
Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
(A) is true but (R) is false
Both (A) and (R) are false

Short Solution (Best for NEET):

To solve this problem, we apply the core principles of Refraction by Prism. Understanding the underlying formula is key to arriving at the correct answer below:

Deviation is given by (delta = (mu-1)A), where (mu), is the relative refractive index. When immersed in water, (mu_{gw} = mu_g/mu_w), which is less than (mu_{ga} = mu_g), (refractive index w.r.t. air). A smaller (mu), leads to a smaller deviation. Both assertion and reason are true, and R correctly explains A.

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