Question

Arrange the following in the correct order as the angle of incidence in a denser medium is gradually increased. (A) The refracted ray bends away from the normal. (B) The refracted ray grazes along the surface of separation. (C) The light is totally reflected back into the denser medium. (D) The ray passes undeviated when incident normally. Choose the correct answer from the options given below:

• A. (A), (D), (B), (C)
• B. (D), (B), (A), (C)
• C. (D), (A), (B), (C)
• D. (A), (C), (B), (D)

Hint:

For light travelling from a denser to a rarer medium: \[ i=0^\circ \Rightarrow \text{No deviation} \] \[ i=i_c \Rightarrow \text{Refracted ray grazes the surface} \] \[ i>i_c \Rightarrow \text{Total Internal Reflection} \] Remember the sequence: \[ \text{Normal incidence} \rightarrow \text{Refraction} \rightarrow \text{Critical angle} \rightarrow \text{TIR} \]

Answer 1

The Correct Option is C

Concept: When light travels from a denser medium to a rarer medium and the angle of incidence is gradually increased:
• At normal incidence, the ray passes undeviated.
• For angles less than the critical angle, the refracted ray bends away from the normal.
• At the critical angle, the refracted ray grazes along the interface.
• For angles greater than the critical angle, total internal reflection occurs.

Step 1:Consider normal incidence. When \[ i=0^\circ \] the ray passes undeviated. \[ (D) \]

Step 2: Increase the angle of incidence. For \[ 0^\circ<i<i_c \] the refracted ray bends away from the normal. \[ (A) \]

Step 3: Reach the critical angle. At \[ i=i_c \] the refracted ray grazes along the surface. \[ (B) \]

Step 4: Increase beyond the critical angle. For \[ i>i_c \] total internal reflection occurs. \[ (C) \]

Step 5: Write the correct sequence. \[ (D)\rightarrow(A)\rightarrow(B)\rightarrow(C) \] \[ { (D),\ (A),\ (B),\ (C) } \] Hence, the correct option is \[ {(C)} \]