Monochromatic light of wavelength 667 nm is produced by a helium-neon laser. The power emitted is 9 mW. The number of photons arriving per second on the average at a target irradiated by this beam is

9 x 10¹⁷

3 x 10¹⁶

9 x 10¹⁵

3 x 10¹⁹

Name: Wired Faculty - The Best Learning App
Rating: 4.6 (1864 reviews)

Solution

3 x 10¹⁶

Here space straight lambda space equals space 667 space straight x space 10 to the power of negative 9 end exponent space straight m comma space straight P space equals space 9 space straight x space 10 to the power of negative 3 end exponent space straight W Power space equals space energy over time space equals space nhc over λt equals space Nhc over straight lambda Where space straight N space is space number space of space photons space emitted space per space sec. rightwards double arrow space straight N space equals space fraction numerator straight p space straight x space straight lambda over denominator hc end fraction space equals space fraction numerator 9 space straight x space 10 to the power of negative 3 end exponent space straight x space 667 space straight x space 10 to the power of negative 19 end exponent over denominator 6.6 space straight x space 10 to the power of negative 34 end exponent space straight x space 3 space straight x space 10 to the power of 8 end fraction space equals space 3 space straight x space 10 to the power of 16 space straight s

For Daily Free Study Material Join wiredfaculty