物理 2007 年 DSE、CE 選擇題（第 2 頁）

11.

Convex lens with foci F and F', incident ray AB and possible emergent rays P, Q, R and S

$F$ and $F'$ are the foci of the above lens and $AB$ is an incident ray. Which light ray best represents the emergent ray ?

12.

Light ray in water incident on an air bubble with possible emergent rays W, X, Y and Z

A light ray is incident from water onto an air bubble as shown above. Which light ray best represents the emergent ray ?

13.

Figure (a) shows a light ray travelling from air into medium $X$ . The angle of incidence is $50^\circ$ and the angle of refraction is $r$ . Another light ray travelling from medium $X$ to air is shown in Figure (b). The angle of incidence is $35^\circ$ and the angle of refraction is also equal to $r$ . What is angle $r$ ?

$Figure (a): ray from air into medium X at 50 degrees, refraction angle r. Figure (b): ray from medium X to air at 35 degrees, refraction angle r$

14.

The figure shows a web cam. A web cam typically includes a lens and an image sensor. The function of the image sensor is similar to that of a film in a conventional camera. The image is formed on the sensor and is then digitised. Which of the following statements is/are correct ?

(1)The lens is a convex lens.

(2)The lens is a concave lens.

(3)Image formed on the image sensor is real.

15.

Light from a source passing from air to water through a slit

Light travels from air to water through a slit as shown above. Which of the properties of the light in water remain(s) unchanged ?

(1)direction of travel

(2)speed

(3)frequency

16.

Which of the following phenomena demonstrate(s) that light is an electromagnetic wave ?

(1)Light bends when it travels across a boundary from one medium into another.

(2)Light reflects when it meets a polished metal surface.

(3)Light can travel from the Sun to the Earth.

17.

A household circuit breaker is marked ' $220$ V, $15$ A'. Now an electric iron rated ' $220$ V, $1100$ W' and a cooker rated ' $220$ V, $550$ W' are connected to a mains socket. How many light bulbs rated ' $220$ V, $100$ W' at most can still be connected in parallel to the mains without triggering the circuit breaker ?

18.

Spheres P and Q hanging apart, and spheres R and S hanging close together, on threads of the same length

In the above figures, $P$ , $Q$ , $R$ and $S$ are identical light conducting spheres and they are hanging freely by insulating threads of the same length. Which of the following deductions is/are correct ?

(1)

P

and

Q

must carry like charges.

(2)

R

and

S

must carry unlike charges.

(3)

P

and

Q

must carry the same amount of net charges.

19.

Resistors 8 ohm and 2 ohm in series in parallel with 6 ohm and 4 ohm in series between X and Y

In the circuit shown, a voltage of $10$ V is applied across $XY$ . What is the current passing through the $8\ \Omega$ resistor ?

20.

Battery with 1 ohm and 5 ohm resistors in parallel in series with a 2 ohm resistor and an ammeter

If the ammeter in the above circuit reads $3$ A, what is the voltage of the battery ?