+91-8076753736[email protected]
logo
logo
-->

Work, Energy And Power

Question
CBSEENPH11020570
Wired Faculty App

A 200 W sodium street lamp emits yellow light of wavelength 0.6 um. Assuming it to be 25% efficient in converting electrical energy to light, the number of photons of yellow light it emits per second is

  • 1.5 x 1020

  • 6 x 1018

  • 62 x 1020

  • 3 x1019

Solution

A.

1.5 x 1020

 Efficient power P= 
P equals space straight N over straight t space equals space fraction numerator h c over denominator lambda end fraction space equals space 200 space x 0.25 N over t space equals space 50 space x fraction numerator lambda over denominator h c end fraction space equals space 1.5 space x space 10 to the power of 20 space equals fraction numerator 50 space x 0.6 space x space 10 to the power of negative 6 end exponent over denominator 6.6 space x space 10 to the power of negative 34 end exponent space x space 3 x space 10 to the power of 8 end fraction space equals space 1.5 space x space 10 to the power of 20

Some More Questions From Work, Energy and Power Chapter

 Define the term electricity?

Write the SI unit of gravitational constant?

Define the unit joule.

What are different units of energy?

What is watt?

Define watt.

How many joules are there in one eV?

What is the relation between kWh and Joule?

Mock Test Series

Mock Test Series

NCERT Sample Papers

Entrance Exams Preparation