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The following 2 comments and questions have been sent in. They are listed according to date.

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• Can looking into a microwave oven harm you?
• Why is the sky blue?

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Can looking into a microwave oven harm you?

Question

March 6, 2009

This question comes up because someone commented on how they avoided looking at a microwave oven to reduce exposure of their retinas to the microwaves. Are radio waves emitted by a microwave oven (freq. = 10^11 Hz) focused by the lens in the human eye? How does the speed of microwaves and X-rays through glass and similar transparent materials compare with the speed of light through those same materials?

Mac - USA

17398

Answer

The mesh screen in the microwave oven window is a size that blocks out any microwaves, making it safe to look inside. But if the glass or the mesh in the window is cracked, there is that danger of leakage.

Microwaves are shorter than radio waves. Neither is focused by the lens of the eye.

The speed of light through a material like glass varies with the wavelength. X-rays are much shorter and microwaves are longer than visible light. I don't have any numbers on their speed in glass.

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Why is the sky blue?

Question

June 9, 2008

why do we see blue sky during the day but during dawn the sky turns into red or orange in colour? can you explain to me why is this phenomenon occurs... thnx :D

naqib - Malaysia

16066

Answer

Dust particles in the atmosphere are of the size that they reflect blue at an angle more that other colors. As the Sun is above and you look away from it, the sky looks blue because your are seeing those reflected rays. During dawn, the light must travel through more atmosphere and the light is reflected at a different angle. This causes it to appear red or yellow. The whole effect is called Rayleigh scattering.

For a good detailed explanation, see: http://www.sciencemadesimple.com/sky_blue.html

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