Because of barriers and obstructions you can see only a tiny fraction of a standing wave on a string. You do not know, for instance, how long the string is. All you know is that the speed of waves on the string is 100 m/s and that the distance ? in the sketch is 10 cm. All you know is that the speed of waves on the string is 100 m/s and that the distance ? in the sketch is 10 cm. Can you determine the frequency of the standing wave?

1. Sure, the frequency is 500 Hz.
2. No, you have no way to know the number
of nodes, for instance.
3. Sure, the frequency is 10 Hz.

Sure, the frequency is 500Hz

Explanation:

Sure, the frequency can be calculated. The needed information which is the speed and wavelength of the wave are known.

Wavelength is the distance between two successive crest and trough of a wave.

Using the relationship

V = fλ

V is the speed of wave

F is the frequency

λ is the wavelength

f = v/λ

Given v = 100m/s, λ = 10cm/0.5 = 20cm

20cm = 0.2m

f = 100/0.2

f = 500Hertz

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.