which of these events is an example of the doppler shift? the amplitude of a wave on a string increases as the frequency decreases. the amplitude of sound from a tuning fork decreases due to damping. the frequency of light from a star increases as it moves toward us. the intensity of an electromagnetic wave increases with the field strength. the velocity of an electromagnetic wave changes as its medium changes.

i'm just gonna leave this comment here, so i can get a challange done-

explanation:

a solenoid is created by wrapping a l = 90 m long wire around a hollow tube of diameter d = 4.5 cm.   the wire diameter is d = 0.9 mm.   the solenoid wire is then connected to a power supply so that a current of i = 9 a flows through the wire.

randomized variablesl = 90 m

d = 4.5 cm

d = 0.9 mm

i = 9 a                                          

write an expression for the number of turns, n, in the solenoid. you do not need to take into account the diameter of the wire in this calculation.

calculate the number of turns, n, in the solenoid.

write an expression for the length of the solenoid (l2) in terms of the diameter of the hollow tube d.

calculate the length of the solenoid (l2)   in meters.

calculate the magnitude of the magnetic field at the center of the solenoid in teslas.

explanation: