What are the basic properties of electromagnetic radiation? Light is a part of o

Question

What are the basic properties of electromagnetic radiation? Light is a part of our everyday life. Having a basic understanding of its properties is important for us to understand what we see. To begin with this we will start with identifying what you already know. 1. What causes light to have different colors? Use physics to explain your answer. 2. Can light be used to cancel out light? Use physics to explain your answer. (ex. Can light be used like sound is in a pair of noise canceling headphones.) 3. If you shine different colored light on a table what happens to the color of the table? Use physics to explain your answer. 4. If you can see inside a room that means that light exists in the room. Does all the light come only from the light bulbs. Use physics to explain your answer. 5. What causes shadows? Use physics to explain your answer.

Explanation / Answer

1] The colors we perceive have different wavelengths and it is this which gives them color. Also, color is property assigned by the cones cells of our eyes which are responsive to wavelength of light ranging from 400nm to 700 nm.

2] Light of a given wavelength has electric field oscillating sinusoidally in a particular plane. If another beam of same wavelength travels in the same direction and has zero phase difference with the first light beam then the light will interfere and the intensity of the light will be dependent of whether the interference was constructive or destructive.

If the waves were out of phase (maintained a phase difference of half wavelength) then the light can be cancelled out.

3] Assuming the table has a unique color throughout, the color of the table tells that it is this color which is reflected by the table and the rest are absorbed by it. So if any color other than the color of the table is incident on it, it will be absorbed hence giving the impression that the table is black (since the table can only be seen if the light of its wavelength illuminates it thereby reflecting it to our eyes).

4] Much of the stray light in a room also comes from light being constantly reflected from the objects inside the room which themselves are illuminated by the light bulbs.

5] Shadow is a dark area produced by an opaque object on a surface due to the absence of light on the rear end of the object. This happens because the rear end of the object is not illuminated by light hence it cannot reflect any light thereby appearing to be dark.

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