What is the critical angle in optics?
A
The angle of incidence at which refraction is maximum
B
The angle of incidence for which the refracted ray makes 90° with the normal
C
The angle of reflection at which total reflection occurs
D
The angle between incident and reflected ray
Analysis & Theory
Critical angle is the angle of incidence in the denser medium at which the refracted ray in the rarer medium makes 90° with the normal.
When does total internal reflection occur?
A
When light passes from rarer to denser medium
B
When angle of incidence is less than critical angle
C
When light passes from denser to rarer medium and incidence > critical angle
D
At any angle of incidence
Analysis & Theory
Total internal reflection occurs only when light travels from denser to rarer medium and the angle of incidence exceeds the critical angle.
Which of the following is the condition for total internal reflection?
B
n₁ > n₂ and angle of incidence > critical angle
D
Angle of incidence < critical angle
Analysis & Theory
n₁ and n₂ are refractive indices. TIR occurs when light goes from higher to lower refractive index and incidence exceeds critical angle.
What is the formula for the critical angle?
Analysis & Theory
Critical angle C is given by sin C = n₂ / n₁ (n₁ > n₂).
Which phenomenon is based on total internal reflection?
Analysis & Theory
Optical fibers use TIR to guide light with minimal loss over long distances.
What happens to light at incidence angle equal to the critical angle?
B
It is totally reflected
C
It refracts along the boundary
Analysis & Theory
At the critical angle, the refracted ray travels along the boundary (90° to the normal).
If n₁ = 1.5 (glass) and n₂ = 1 (air), what is the critical angle?
Analysis & Theory
sin C = n₂/n₁ = 1/1.5 = 0.6667 → C = 41.8°.
Which of the following is NOT a condition for total internal reflection?
A
Light must travel from denser to rarer medium
B
Angle of incidence > critical angle
C
Refractive index of denser medium > rarer medium
D
Light intensity must be high
Analysis & Theory
Light intensity does not affect TIR; only the medium and angle conditions matter.
In optical fibers, total internal reflection helps to:
Analysis & Theory
TIR in fibers prevents light from escaping, ensuring efficient transmission.
Total internal reflection is possible for which type of waves?
C
All waves that can undergo refraction
D
Only electromagnetic waves in vacuum
Analysis & Theory
TIR can occur for any wave (light, sound, microwaves) that can be refracted and satisfies TIR conditions.