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[cvxfreak]

Draw a ray diagram of a plane mirrorto show that if you want to see yourself from your feet to the top of your head, the mirror must be at least half your height.

Does the result depend on the distance of the mirror? Justify your answer.

;_;

I'm so lousy in physics. Someone help!

 

[Dan]

Umm, I don't know about the diagram, but the distance between the person and the mirror most certainly matters. As that distance decreases, the mirror's height has to increase towards the practical maximum of the person's height. As the distance increases, the mirror's height can shrink and still fit the entire image in.

Right?

 

[GG-Duo]

hrm... maybe it involves how the ray of incidence and reflection are symmetric to each other.
try drawing a mirror on one end, then drawing a ray from the top of mirror to the figure's eye, and then drawing a symmetric ray across the horizontal and see what happens.

ugh. it's been so long....... are you in high school? cuz that's how i would do it in HS :/

 

[Hsieh]

When light hits a plane mirror, it is reflected back at the same angle as before. If your body is parallel to the mirror, then the light will hit your eye at the same angle that the ray originally left your body from. This forms an isosceles triangle with your body as the base of the triangle. Then the point of contact where the ray of light is perpendicular to half way between the object that you're seeing and your eye. This means minimum boundaries of the mirror are halfway to the top of your head and halfway to the bottom of your feet.

 

[sc0la]

Meh. The question is so poorly worded and open ended.

 

[cvxfreak]

Ah... thanks for the explanation!

I totally understand it now... this was an extra credit question, and judging from the difficulty for the class in the future, I'm going to need it.

 

[GG-Duo]

that was extra credit? that's kinda simple. open-ended, but not that hard...

 

[Nerevar]

Umm, I don't know about the diagram, but the distance between the person and the mirror most certainly matters. As that distance decreases, the mirror's height has to increase towards the practical maximum of the person's height. As the distance increases, the mirror's height can shrink and still fit the entire image in.

Right?

No.