Question

A strip of sodium metal is bombarded by violet light (wavelength = 410 nm) at a rate of 10,000 photons per second, which causes a steady stream of electrons to be ejected from the metal, via the photoelectric effect. The minimum energy required to eject an electron from sodium is 4.41 ×10-19J. What will happen if the sodium is now bombarded by red light (wavelength = 700 nm) at a rate of 10,000 photons/second?

Answer 1

Answer:

The minimum energy required to eject an electron from sodium will be bigger.

Explanation:

red light has a higher wavelength, that mean that the energy that emitted is lower in comparison with the violet light.

If the rate of the photons is the same, 10,000 photons per second, that  means that the required energy to take an electron need to be bigger to have the same effect.

Hope this info is useful.

Answer 2

The question is incomplete, the complete question is:

A strip of sodium metal is bombarded by violet light (wavelength = 410 nm) at a rate of 10,000 photons per second, which causes a steady stream of electrons to be ejected from the metal, via the photoelectric effect. The minimum energy required to eject an electron from sodium is 4.41 ×10-19J. What will happen if the sodium is now bombarded by red light (wavelength = 700 nm) at a rate of 10,000 photons/second? (a) The number of electrons ejected per second will decrease(b) The number of electrons ejected per second will increase(c) Electrons will no longer be ejected (d) The rate of ejected electrons will remain constant, but the kinetic energy of the ejected electrons will decrease(e) The rate of ejected electrons will remain constant, but the kinetic energy of the ejected electrons will increase

Answer:

Electrons will no longer be ejected

Explanation:

Now let us look at the question critically. We have been told that the work function of the metal is 4.41 ×10-19J and only photon of energy greater than this can eject electrons from the sodium metal.

Now, let us consider the energy of the violet light:

From E= hc/λ where λ= 410×10^-9 m

E= 6.6×10^-34 ×3×10^8/410×10^-9

E= 19.8×10^-26/410×10^-9

E= 4.8×10^-19J

This energy is greater than the work function of the metal hence electrons are emitted.

How about the red light of λ= 700×10^-9 m

E= hc/λ

E= 6.6×10^-34 ×3×10^8/700×10^-9

E= 2.8×10^-19 J

This energy is less than the work function of sodium metal hence no electrons are emitted.