PHYSICS!!!!!!help!!!!

Lisa

2012-01-02 1:07 am

1. You are taking a flask photograph of your friends at a party. Your friends are standing with a wall mirrow behind them. How can you take a better photograph?

2. A man stands 3m from a plane mirrow holding a mirror.
(a)To take a sharp photograph of his image. what distance setting of the camera should the man use?

(b) can he obtain a sharp photograph if he uses an auto-focus camera( which focuses on the object diretly in front?) Explain briefly.

3. A goldfish in a tank appears nearer and bigger than it really is to the girl. In contrast, how does the girl appear to the goldfish?Why?

4. Explain the working principle of grond glass windows.

5. Diamonds can lose their brilliance if a thin film or oil seeps behind the stone due to poor mounting. Briefly explain this terms of the critical angle for a diamond-oil interface. It is given that the refractive index indices of diamond and oil are 2.42 and 1.40 respectively)

THANKS!!!!!!!!!!

回答 (1)

天同

2012-01-23 7:57 am

✔ 最佳答案

1. Place the camera at an angle to the wall mirror, such that light coming from the flash is reflected to the other side.

2. (a) Focus the camera at 3 metres behind the mirror, i.e. 6 metres from the man where the position of his image is located.

(b) No. The object in front of the camera is the mirror. The auto-focus device will focus at the mirror.

3. By the principle of Reversibility of Light, the girl appears smaller and farther away than she should be.

4. Ground glass windows have rough surfaces that leads to diffusive reflection and transmission. Hence, the windows appear translucent instead of transparent.

5. The introduction of the oil film increases the critical angle of diamond from 24 degres to 35 degrees. Hence, the occurence of total internal reflection decreases. That is tosay, less amount of light undergoes total internal eflection and the diamond thus appears less bright.

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