3 years ago

Why do reflecting telescopes usually have a secondary mirror in addition to a primary mirror?

1 answer:

8 0

Once the starlight or moonlight comes down the tube and hits the big main mirror at the bottom, it's reflected, and heads back up the tube, along the same way it came in. But if you're looking through an eyepiece, the eyepiece is on the SIDE of the tube. So you need another small mirror, to catch the focused light before it goes up out of the tube, and send it sideways to the eyepiece.

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24. An elevator is moving vertically up with an acceleration a. The force exerted on the floor by a passenger of mass m is

Wewaii [24]

Given :-

An elevator is moving vertically up with an acceleration a.

To Find :-

The force exerted on the floor by a passenger of mass m .

Solution :-

As the man is in a accelerated frame that is non inertial frame , we would have to think of a pseudo force .

The direction of this force is opposite to the direction of acceleration the frame and its magnitude is equal to the product of mass of the concerned body with the acceleration of the frame .

For the FBD refer to the attachment . From that ,

$\implies Weight_{apparent}= mg + ma$