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**gourish****Member**- Registered: 2013-05-28
- Posts: 113

if a pair of mirrors are placed together making an angle θ with each other and if a ray of light parallel to first mirror reflects from the second mirror which after 2 successive reflections becomes parallel to second mirror. then find the angle θ

"The man was just too bored so he invented maths for fun"

-some wise guy

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**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,471

Just making a diagram.

Bob

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

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**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,471

OK got it.

The first mirror is AB and the second BC.

The red lines show the ray reflecting off AB, then off BC.

When a ray reflects off a mirror the angle of incidence = the angle of reflection . On my diagram that amounts to saying that the angle marked 1 is the same as the angle marked 2. Also you have parallel lines so you should be able to say something about angle 3.

Keep applying the reflection and parallel rules to find the relationship between angles 1, 2, 3, 4 and 5. That will answer the question.

Bob

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

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**gourish****Member**- Registered: 2013-05-28
- Posts: 113

well 1=3=4 but what about 2 and 5?

"The man was just too bored so he invented maths for fun"

-some wise guy

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**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,471

eg. When the ray reflects for the first time it reflects off at the same angle that it struck the mirror. So angle 1 = angle 2.

Bob

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

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**gourish****Member**- Registered: 2013-05-28
- Posts: 113

thanks that was enough to find the answer... any ideas where i can practice more of these kind of optics related problems?

"The man was just too bored so he invented maths for fun"

-some wise guy

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**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,471

Try this:

A shape is reflected in a mirror and the image is reflected in a second, parallel mirror. What transformation takes the original shape onto the final image?

Bob

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**gourish****Member**- Registered: 2013-05-28
- Posts: 113

i didn't understand your question.... the "What transformation takes the original shape onto the final image?" part is bit confusing what do i need to find here...?

"The man was just too bored so he invented maths for fun"

-some wise guy

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**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,471

Try drawing a diagram.

Bob

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