Answer:
For destructive interference phase difference is
where n∈ Whole numbers
Explanation:
For sinusoidal wave the interference affects the resultant intensity of the waves.
In the given example we have two waves interfering at a phase difference of 
would lead to a constructive interference giving maximum amplitude at at the RMS value of the amplitude in resultant.
Also the effect is same as having a phase difference of 
because after each 2π the waves repeat itself.
<em>In case of destructive interference the waves will be out of phase i.e. the amplitude vectors will be equally opposite in the direction at the same place on the same time as shown in figure.</em>
They have a phase difference of 
or which is same as 
Generalizing to:
a phase difference of where n∈ {W}
{W}= set of whole numbers.
Answer:
When the metal wire in an incandescent lightbulb glows when the light is switched on and stops glowing when it is switched off, this is an example of resistance, which provides light and heat.
Explanation:
<h2>
Answer: a.The mirrors and eyepiece of a large telescope are spring-loaded to allow them to return quickly to a known position. </h2>
Explanation:
Adaptive optics is a method used in several astronomical observatories to counteract in real time the effects of the Earth's atmosphere on the formation of astronomical images.
This is done through the insertion into the optical path of the telescope of sophisticated deformable mirrors supported by a set of computationally controlled actuators. Thus obtaining clear images despite the effects of atmospheric turbulence that cause the unwanted distortion.
It should be noted that with this technique it is also necessary to have a moderately bright reference star that is very close to the object to be observed and studied. However, it is not always possible to find such stars, so a powerful laser beam is used to point towards the Earth's upper atmosphere and create artificial stars.
It looks blue as it is only reflecting blue light
