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Wolgwang

09:17

The number of reflections including the initial one will be number of such triangle with base d in the upper plate + 1?

We can verify this for small n:

n                      reflection:
1                      2
2                      3
3                      4

So answer to this should be 31 , no?

@JohnRennie Can you take a look here 👆 when you get time :)

John Rennie

I guess it depend on whether you count the very last reflection where I've drawn the blue box. I would count it, and then I get 31 as well. If you don't count it then you get 30.

Wolgwang

09:38

@JohnRennie I think that must be the reason why it is not in the options.

John Rennie

Does the answer key give B?

Wolgwang

Yes.

John Rennie

OK. It depends on whether you take the length of the mirror to be an open or closed interval :-)

I still think 31 is correct, but of the options given only 30 could be correct.

Wolgwang

@JohnRennie When is the spherical aberration less in plano convex surface? When the plane side face object or vice versa?

I think when object face plane surface as there will be refraction(angle change) once.

But the answer is opposite...

John Rennie

I don't know ...

Wolgwang

09:44

I think I have to learn it as a fact ...

Q: Why do plano-convex lenses reduce spherical aberation?

I keep reading this in comparisons of different kinds of lenses but I don't understand why the flat side would change the amount of spherical aberration if the focal length still has to be the same?

12 hours later…

HNQ

21:47

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HNQ

22:38

Q: Energy Conservation in electromagnetism

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