Urgent! a wavelength is a) the number of waves per second b) the distance between two crests of a wave c) the distance from the crest to the trough of a wave d) the distance from the crest of one wave to the trough of the next wave

Modern physics a photon emitted from an excited hydrogen atom has an energy of 3.02 electron volts. which electron energy-level transition would produce this photon? a. n=1 to n=6 b. n=2 to n=6 c. n=6 to n=1 d. n=6 to n=2 i chose b but the correct answer is d can someone tell me why? and what's the difference?

For the car in the picture ,in which direction is the normal force? -into the screen -down -out of the screen -up

How do the kidneys affect homeostasis