Question

two lamps of 1 CP and 60 CP luminous intensity are separated by 100cm find where on the line joining them a photometer screen should be placed so that its both ends are illuminated equally​

Answer 1

Answer:

At what distance from the photometer must a third lamp of 27 c.p. be placed in order that both sides of the photometer may be equally ...

Answer 2

Two lamps of 1 CP and 60 CP luminous intensity are seperated by 100 cm.

find where on the line joining them a photometer screen should be placed so that its both ends are illuminated equally.

solution : let distance between 1CP and photometer screen is x cm.

then distance between 60CP and photometer screen is (100 - x) cm.

if ends are illuminated equally,

(1 CP)/(x cm)² = (60 CP)/(100 - x)²

⇒1/x² = 60/(100 - x)²

⇒1/x = 2√15/(100 - x)

⇒100 - x = 2√15x

⇒x = 100/(1 + 2√15) = 11.43 cm

Therefore the screen should be placed 11.43 cm from the first lamp of 1 CP luminous intensity.