As an analogy to wave packets, consider an "automobile packet" that occurs near the scene of an accident on a freeway. The phase speed is analogous to the speed of individual automobiles as they move through the backup caused by the accident. The group speed can be identified as the speed of the leading edge of the packet of cars. For the automobile packet, which of the following is true? a. The group speed is greater than the phase speed. b. The group speed is the same as the phase speed c. The group speed is less than the phase speed

c. The group speed is less than the phase speed.

Explanation:

For an individual the speed is given by v phase = w/k

w is angular frequency and k is wave number.

This is called phase speed. Group speed is the speed of wave packet.The rate of advance of a crest on a single wave point which is fixed phase.

you'd use the equation that establishes a relationship between  energy  and  wavelength, which looks like this

e=h⋅cλ, where

λ  - the wavelength of the photon; c  - the speed of light, usually given as  3⋅108m/s; h  -  planck's constant, equal to  6.626⋅10−34j s

plug the value you were given for the energy of the photon in the above equation to get the wavelength

e=h⋅cλ⇒λ=h⋅ce

λ=6.626⋅10−34js⋅3⋅108ms−1.257⋅10−24j=1.581⋅10−1m