Which of the following scenarios about the de Broglie wavelength of an object is not possible?
- A 100 m sprinter has a wavelength of about 10-36 m.
- A stationary electron has wavelength of infinite length.
- An elephant with an associated wavelength equals zero.
- A Sumo wrestler has wavelength smaller than a child when both moves with the same speed.
λ = h / mv
For option 3, Zero wavelength means its speed is infinite – not possible.
In the production of laser, a two-level system is not preferred because
- there are not many elements with only two level system.
- too many atoms will remain in the excited state for long duration.
- the energy difference between the two levels is too little for photons to be emitted.
- population inversion will not be possible as atoms arrive in the excited level at the same rate as they leave.
Explanation found here: https://www.miniphysics.com/how-laser-works.html