Stimulated Emission

Mr. Andersen explains stimulated emission in AP Physics Essentials video 137. He introduces the concept using red light and describes how photons can be directed coherently to form a laser. The video covers stimulated absorption and emission, using energy diagrams to illustrate photon interactions. It explains how lasers are built by reflecting photons with mirrors. A PHET simulation demonstrates these concepts, showing how wavelength affects energy levels and photon coherence. The video concludes by reinforcing the connection between energy levels and photon absorption or emission.

What is the primary characteristic of a laser compared to regular light?

• It emits light of multiple colors.

• It emits light with varying frequencies.

• It emits light in multiple directions.

• It emits light coherently in one direction.

What happens during stimulated emission when an atom at a higher energy level is hit by a photon?

• The atom emits a photon of a different frequency.

• The atom emits two identical photons.

• The atom remains at the same energy level.

• The atom absorbs the photon and moves to a lower energy level.

In the context of stimulated emission, what must match between the photon and the energy states of an atom?

• The speed of the photon.

• The color of the photon.

• The wavelength or frequency of the photon.

• The size of the photon.

How can the process of stimulated emission be amplified to create a laser?

• By using a single atom repeatedly.

• By using photons of different wavelengths.

• By using mirrors to reflect photons back and forth.

• By increasing the temperature of the atoms.

What role do mirrors play in the construction of a laser?

• They increase the energy of the photons.

• They absorb excess photons.

• They reflect photons to build up coherent light.

• They change the color of the photons.