7. The night of desest is very cold and the day is very
hot
Give reason

1) Sand cannot hold the heat. It acts like a mirror to the sun. During the daytime, it stays warm, and when the Sun is absent it loses all its heat making the nights colder. There's nothing in the desert that can either absorb heat from the sun or hold it on the surface when the sun is set.

2) Deserts are hot primarily because of a lack of water. When the sun shines on the ground, all of the absorbed sunlight goes into raising the ground's temperature. DESERTS ARE COLD AT NIGHT:Because of the lack of water in the ground, and little water vapor in the air, most deserts can get quite cool at night.

3) The temperature in the desert can change drastically from day to night because the air is so dry that heat escapes rapidly at night. The daytime temperature averages 38°C while in some deserts it can get down to -4°C at night. The temperature also varies greatly depending on the location of the desert.

diagram is missing, but i will try to explain your doubt.

answer:

amplitude is the maximum displacement or distance moved on a point of a vibrating body or wave measured from its equilibrium position.it is equal to half the length of vibration path.