A helium-neon laser emits red light having a wavelength of 6.4 times 10^-7 m and

Question

A helium-neon laser emits red light having a wavelength of 6.4 times 10^-7 m and a power of 0.5 mW. How many photons are emitted each second? A photon whose energy is 8.00 times 10^-15 J is scattered off an electron at a 90 degree angle. What is the wavelength of the scattered wave? A photon whose wavelength is = 5.0 times 10^-11 m is scattered straight backward. What is the wavelength of the scattered wave? A neutron has a mass of 1.67 times 10^-27 kg. Its de Broglie wavelength is 1.4 times 10^-10 m. What is its kinetic energy (in eV)?

Explanation / Answer

( 1.)

We know that, for a photon, E = hf and f = c, so E = hc/. Also, P = W/t. If P = 0.5 mW, then we must have enough photons to equal 0.5 mJ/s. So, E = hc/ = 6.6x10-34x 3x108/ (6.4x10-7) = 3.093x10-19 J

If N is the number of photons emitted by the source per second,the power P transmitted in the beam equals N times the energy per photon E, so that P = NE. then

N=P/E =0.5x10-3W/(3.093x10-19 )

= 1.61 x 1015 Photons per seconds

4.)

here E = Kinetic energy of electron

= h / (2mE)1/2

E = 6.65 X 10 -21 joule Answer

2.)

E = hc/

= 2.475 x 10-11 m

As per Compton scattering

= h ( 1 cos )/ mc

= Scatterig angle = 90

= 2.716 x 10-11 m

3.

= Scatterig angle = 180

= 0.241 x 10-11(1-(-1))

= 0.482 x 10-11

= 5.482 x 10-11 m Answer

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