Answer:
2. D. Electrical energy is converted into electromagnetic energy and then into thermal energy
3. B. Longitudinal waves need a medium to travel through.
Step-by-step explanation:
2. Microwave ovens
You plug in the microwave oven into the wall outlet and turn on the switch.
That means that you start by using electrical energy (this eliminates options B and C).
The microwave oven converts electrical energy into microwaves (electromagnetic energy)
.
The microwaves interact with the molecules in the food and cause it to heat up. The electromagnetic energy is converted to thermal energy.
Thus, electrical energy is converted into electromagnetic energy and then into thermal energy.
3. Longitudinal and transverse waves
Sound waves are a good example of longitudinal waves.
They propagate by alternating compressions and rarefactions of the medium in the direction they travel.
Longitudinal waves need a medium to travel through.
A is wrong. Transverse waves can propagate in a vacuum.
C is wrong. Transverse waves do not have compressions and rarefactions. The can travel through a vacuum where there is no matter to interact with.
D is wrong. Longitudinal waves move by creating compressions and rarefactions in the medium they travel through.
