Question

An electric bulb illuminates a plane surface. The intensity of illumination on the surface at a point 2 m away from the bulb is 5 × 10⁻⁴ phot (lumen/cm²). The line joining the bulb to the point makes an angle of 60° with the normal to the surface. The luminous intensity of the bulb in candela (candle power) is(a) 40√3(b) 40(c) 20(d) 40 × 10⁻⁴

Answer 1

An electric bulb illuminates a plane surface. The intensity of illumination on the surface at a point 2 m away from the bulb is 5 × 10⁻⁴ phot (lumen/cm²). The line joining the bulb to the point makes an angle of 60° with the normal to the surface. The luminous intensity of the bulb in candela (candle