Light can be seen as an electromagnetic wave.
What happens when two waves, with the same frequency, superpose is called interference.
If at a certain point two waves arrive both with a crest, we have constructive interference and the amplitudes sum up, reaching the maximum value, resulting in bright spots.
If at a certain point one of the waves arrives with a crest and the other wave arrives with a trough, we have destructive interference, and the two amplitudes cancel out, resulting in dark spots.
Therefore, t<span>he dark bands on the wall are from destructive interference.</span>
The formula for average speed is

So we can just substitute our data.

- its the result
Note: Although the video is not provided in this question, it is not needed to answer the question.
Answer:
B) It does not deflect at all
Explanation:
Since both half shells contain opposite charges, the two shells become electrically neutral when they are brought together and the electroscope discharges. On separating the two half shells again, the needle does not deflect because the half shells have now lost their charges to become neutral.
Answer:
The peak wavelength of the light it irradiates decreases
Explanation:
As the temperature of a blackbody increase, the peak wavelength of the light it radiates decreases, this follows Wien's Law.
A blackbody is an ideal substance that emits all frequencies of light and also has the ability to absorb them as well.
Wiens displacement law, explains that the position of the peak wavelength of the thermal radiation emitted by bodies can change with temperature, and as the temperature increases beyond a certain point, the wavelength begins to reduce. This often changes the colour of the light emitted from heated objects.