Answer: The wave can flip upside down.
Reflection is the bending of a wave when it cannot pass through. For example, plain mirrors which are flat, a ray of light hits the mirror and is reflected from the mirror since it cannot pass through
When reflection occurs the speed and frequency of the wave does not change but the wave is flipped upside down.
The speed does not change because speed is affected by the change in medium the frequency also remains the same since the energy of the wave does not change.
Person standing on A will hear the loudest sound
Explanation:
The intensity of a sound wave (which is proportional to the loudness of the sound) follows an inverse square law, which is:

where
I is the intensity of the wave
r is the distance from the source of the sound
This equation means that the intensity of the sound wave (and therefore, its loudness) is inversely proportional to the square of the distance from the source: therefore,
- As we get closer to the source of sound, the loudness increases
- As we move away from the source of sound, the loudness decreases
Therefore, the person that will hear the loudest sound is the one standing closer to the source, and therefore person A.
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17. a
18. c
19. a
20. c
21. c
The energy of a light wave is calculated using the formula
E = hc/λ
h is the Planck's constant
c is the speed of light
λ is the wavelength
For the ir-c, the range is
<span>6.63 x 10^-34 (3x10^8) / 3000 = 6.63 x 10 ^-29 J
</span>6.63 x 10^-34 (3x10^8) / 1000000 = 1.99 x 10^-31 J
For the ir-a, the range is
6.63 x 10^-34 (3x10^8) / 700 = 2.84 x 10^-28 J
6.63 x 10^-34 (3x10^8) / 1400 = 1.42 x 10^-28 J