Which of the following statements is false?
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a. sound waves are the only waves that reflect.
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b. when a sound wave reflects, some of the initial energy is lost.
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c. an echo is a sound wave reflection.
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d. reflection is when a sound wave bounces off an object.

It is false that sound waves are the only waves that reflect.

Option A

Explanation:

Reflection of the waves means that it is a process when waves hit any object, they bounce off from that object. Sound waves are not the only waves which reflect. Other waves which reflect are infrared waves and the radio waves.

Light waves might move through the material which is known as the process of refraction or might even bounce off the material, hence the light waves may or may not reflect. Thus there are other waves also which reflect from the objects.

mass and volume are the answers you are looking for

scattering of light by tiny particles in air to produce the colors we see on sky, is dependent on the following factors:

(i) wavelength of light

(ii) size of the scattering particle  

(iii) distance traveled by light through the atmosphere.

according to rayleigh's law of scattering, the amount of scattering is inversely proportional to the fourth power of its wavelength. shorter the wavelength, greater is its scattering. hence violet/blue light is scattered more than red.

sun's light is a composite light ( visible light) with wavelengths in the range 400 nm (violet) to 700 nm (red). as sunlight passes through our atmosphere, the molecules of air scatter light according to their wavelengths. during sunrise and sunset, the sun's position is below the horizon. hence light from the sun travels a greater distance in the atmosphere when compared to its position a noon.

as sunlight enters the earth's atmosphere, blue light is scattered away and at the end of its journey in the sky, only red and orange wavelengths remain in the beam.

hence at sunrise and sunset, the sky appears reddish orange.