I/GCSE Physics Question Analysis Topic: Physics - Short Questions
Exam Questions:
1) (a) A mobile phone lies along the principal axis of a concave mirror. Show, with the help of a suitable diagram, the formation of its image. Explain why magnification is not uniform.
(b) Suppose the lower half of the concave mirror's reflecting surface is covered with an opaque material. What effect this will have on the image of the object? Explain.
2) Draw a circuit diagram of a transistor amplifier in CE configuration.
Define the terms:
(i) Input resistance and (ii) Current amplification factor.
How are these determined using typical input and output characteristics?
Answers:
For I/GCSE Physics, you should know:
1) (a) Refer to the figure below:
The portion of the phone at C will create an image of equal size only at that position. Referring to the figure, we see that B'C = BC. On the other hand, the portion of the phone between C and F will create an enlarged image that extends beyond position C. It can be seen that magnification throughout the phone is not uniform, hence naturally the image is not uniform either.
(b) Following the laws of reflection, the height of the entire image will be formed. But, the image intensity is reduced as a result of the surface being covered with an opaque material. This manifests in a less bright image.
2) (i) Input resistance is the ratio of the input voltage to the input current. The input voltage is denoted as Vin and the input current is the differential input current ID.
(ii) Current amplication factor is the ratio of the output current to the input current as it passes its way through an electrical device. Such allows us to know the amount of current gained.
End of analysis. Great!
