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Physics · UNITS AND MEASUREMENT

हिन्दी

Which of the following quantities is dimensionless according to the SI system?

  1. A
    Planck constant
  2. B
    Boltzmann constant
  3. C
    Plane angle and solid angle
  4. D
    Luminous efficacy
View Answer & Solution

Correct answer · Option C

Plane angle and solid angle

Explanation

Both plane angle and solid angle are defined as ratios of similar dimensions (arc/radius and area/radius squared) and are dimensionless quantities.

Related questions

According to the NCERT rounding-off rules, the numbers \( 3.745 \) and \( 3.735 \), when rounded off to three significant figures, become respectively:→A spherical surface area element \( dA = 0.25\text{ m}^2 \) at a distance \( r = 0.5\text{ m} \) from the center subtends a solid angle \( \Omega \). An arc of length \( ds = 0.2\text{ m} \) on a circle of the same radius \( r = 0.5\text{ m} \) subtends a plane angle \( \theta \). The ratio of the numerical value of \( \Omega \) (in steradians) to \( \theta \) (in radians) is:→As illustrated in Fig. 1.1(b), a solid angle \( d\Omega \) is defined as the ratio of intercepted area \( dA \) of a spherical surface to the square of its radius \( r^2 \). A flat circular disc of radius \( R \) is placed perpendicular to the axis at a distance \( d = \sqrt{3}R \) from an apex \( O \). The solid angle subtended by the disc at the apex \( O \) is:→A substance of mass \( 5.74\text{ g} \) occupies a volume of \( 1.2\text{ cm}^3 \). Keeping the significant figures in view, its density should be expressed as:→
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