Question

Which of the following is a unitless and dimensionless quantity ?

• A. Angle
• B. Solid angle
• C. Mechanical equivalent of heat
• D. Refractive index

Answer 1

Answer: (D)

Refractive index

The dimensions of a physical quantity are the powers (or exponents) to which the base quantities are raised to represent that quantity.

Angle and solid angle has radians as units.

Mechanical equivalent of heat has joules as unit

.

Refractive index of a material is a dimensionless number.

$n=c/v$

n $=$ refractive index

c $=$ speed of light in vacuum

v $=$ speed of light in medium