Understanding Light and Momentum

The video begins with a physics joke about light and mass, leading to a discussion on how light can have momentum despite having no mass. The teacher explains that the classical formula for momentum (p = mv) does not apply to light, and introduces special relativity as a framework that allows massless objects like photons to have momentum. The video then provides the formula for calculating the momentum of a photon, which is based on Planck's constant and the wavelength of light. The teacher concludes by emphasizing the importance of using the correct formula for photon momentum.

What was the main reason the teacher's joke confused the students?

• The joke was about a different subject.

• The joke contradicted what they had learned.

• The joke was too complex.

• The joke was not funny.

Why does light have momentum even though it has no mass?

• Because it is made of particles.

• Because it travels at a constant speed.

• Because it is affected by gravity.

• Because of the principles of special relativity.

Which formula should be used to calculate the momentum of a photon?

• p = mv

• p = h/λ

• p = E/c

• p = F*t

What is Planck's constant used for in the photon momentum formula?

• To calculate the momentum of a photon.

• To determine the wavelength of light.

• To calculate the energy of a photon.

• To measure the speed of light.

What is the role of special relativity in understanding light's momentum?

• It provides a loophole for massless objects.

• It explains why light has mass.

• It calculates the energy of light.

• It describes the speed of light.

Why is the momentum of a single photon considered extremely small?

• Because photons are very light.

• Because photons have no mass.

• Because photons travel slowly.

• Because Planck's constant is very small.

What practical application is mentioned for the momentum of light?

• Powering electric cars.

• Heating homes.

• Generating electricity.

• Propelling solar sails.

What is the significance of converting wavelength to meters in the photon momentum formula?

• To ensure accuracy in calculations.

• To match the units of Planck's constant.

• To make the formula easier to understand.

• To simplify the formula.

What does the teacher suggest about using the formula p = mv for photons?

• It is only accurate for slow-moving objects.

• It should never be used for photons.

• It is the best formula to use.

• It is outdated and no longer used.

How does the teacher describe the effect of light's momentum on humans?

• It is unpredictable.

• It is extremely small.

• It is dangerous.

• It is very noticeable.