Question

Assertion :A ray is incident from outside on a glass sphere surrounded by air as shown in fig. This ray may suffer total internal reflection at the second interface. Reason: For a ray going from a denser to rarer medium, the ray may suffer total internal reflection.

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. Assertion is correct but Reason is incorrect
• D. Assertion is incorrect but Reason is correct

Answer 1

The correct option is D Assertion is incorrect but Reason is correct

Refraction at both the surfaces appears as shown in the figure.

From geometry we see that both the angles from normal inside the sphere are equal(r). This results from being angles opposite to equal sides of a triangle.

Applying Snell's Law at both the surfaces gives,

$\sin i=\mu \sin r$ (Surface 1)

$\mu \sin r=\sin e$ (Surface 2)

Hence we see $i=e$ which means that total internal reflection does not take place.

However, Statement 2 is true. Total internal reflection takes place when a ray of light goes from denser to rarer medium, when incident with an angle greater than a critical angle. But this does not take place in the above case.