Answer:
<h2>
B. Switch</h2>
Explanation:
<u>A device designed to open or close a circuit under controlled conditions is called a switch. The terms “open” and “closed” refer to switches as well as entire circuits. An open switch is one without continuity: current cannot flow through it.</u>
<h2><u>
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Qualitative data gives the information of quality which can not be measured in numbers. For example: Color of eyes, softness of skin.
Quantitative data is information of quantity that can be represented in numbers. For example length and mass of any object.
Zinc is a silver-gray metal is a qualitative data, here silver gray color is quality of zinc metal which can not be measured in numbers.
Chlorine has a density of 3.2 g/L is a quantitative data. The value of density can be compared with other elements by comparing the numbers.
Gallium is not found in nature is neither qualitative nor quantitative.
Nitrogen has a melting point of –210.00 °C is a quantitative data because this is expressed in numbers.
Aluminum is a solid is a qualitative data because it tells about the state of element which can not be measured in numbers.
Answer:
The refractive index of glass, 
Solution:
Brewster angle is the special case of incident angle that causes the reflected and refracted rays to be perpendicular to each other or that angle of incident which causes the complete polarization of the reflected ray.
To determine the refractive index of glass:
(1)
where
= refractive index of glass
= refractive index of glass
Now, using eqn (1)



Answer:
Light does not need a medium to travel travel through, but since waves must have a medium to vibrate, sound is not created where no air is present.
Explanation: