Question 1

Which is/are source(s) of light?
A  sun
B  star
C  lamp
D  moon

Accepted Answer

3. A, B and C only. The sun, stars and lamps produce their own light, so they are light sources. The moon does not produce its own light; it reflects sunlight, so it is not a light source. Therefore the answer is A, B and C only.

Question 2

Which shadow could not be formed by the ceramic mug below?

Accepted Answer

2. An unfilled circular ring outline. A ceramic mug is opaque, so it blocks all light and produces a solid (filled) shadow. A ring-shaped (hollow outline only) shadow would mean the centre lets light through, which an opaque mug cannot do. The mug-with-handle silhouette, the circle-with-handle (top view), and a square (side view of a square block-like profile) are all possible solid shadows, but the unfilled ring is not.

Question 3

When Jamie stood behind the wall, she could not see her plant. Which of the following explains why Jamie could not see her potted plant?

Accepted Answer

3. The wall did not allow light to pass through.. Jamie can only see the plant when light reflected off the plant enters her eyes. The wall is opaque and does not allow light to pass through, so the reflected light from the plant is blocked and cannot reach her eyes.

Question 4

An object is placed at the centre with four torches. Which two torches are switched on to form the shadows shown in the diagram above?

Accepted Answer

1. P and R. Shadows form on the side opposite to the light source. The diagram shows shadows of the cylindrical object extending to the right and downward (towards corners Q and S). This means light is coming from the opposite corners — torches P (top-left) and R (bottom-left)... but careful inspection shows the shadows are cast towards the bottom-right of the cylinder, meaning the light must come from the top-left and similar direction. The two torches whose light would form those shadows are P and R (both on the left side projecting light rightwards).

Question 5

Study the diagram below. What could you do to obtain a larger shadow of the cone on the paper?
A  move torch towards cone
B  move paper towards torch
C  move cone away from paper
D  move torch away from paper

Accepted Answer

1. A and B only. A shadow becomes larger when the object blocks more of the light spreading out. Moving the torch closer to the cone (A) means the cone blocks more of the diverging light rays, making a larger shadow. Moving the cone away from the paper (C) — i.e. closer to the torch — also makes the shadow larger. Options B and D would make the shadow smaller.

Question 6

Winnie was able to see the flame when she arranged the holes on the cardboards A, B and C in a straight line as shown below. When she moved cardboard B to the left, Winnie could not see the flame. Which of the following explains why Winnie could not see the flame?

Accepted Answer

1. Light travels in straight lines.. Light travels only in straight lines. When the three holes on cardboards A, B and C are aligned, light from the flame passes through all three holes straight into Winnie's eye. When cardboard B is moved sideways, its hole is no longer aligned with the others, so light from the flame can no longer travel in a straight path to her eye.

Question 7

Which is/are source(s) of heat?
A  fire
B  sun
C  mirror
D  lighted bulb

Accepted Answer

4. A, B and D only. Fire, the sun and a lighted bulb all produce heat on their own and are heat sources. A mirror only reflects heat and light; it does not produce heat itself. Therefore A, B and D only are heat sources.

Question 8

Which statement about heat is correct?

Accepted Answer

4. Heat is a form of energy.. Heat is a form of energy that flows from a hotter object to a cooler one. It has no mass, cannot be seen, and does not occupy space (those are properties of matter, not energy).

Question 9

Farah placed a metal spoon in her cup of hot tea. She then left her cup of hot tea on the table for five minutes as shown below. Which of the following describes what happened to the cup, tea and spoon during the five minutes?

Accepted Answer

2. cup: gained heat; tea: lost heat; spoon: gained heat. Heat flows from hotter objects to cooler ones. The hot tea is hotter than the cup and the spoon, so heat flows from the tea to the cup and to the spoon — the tea loses heat, while the cup and the spoon gain heat.

Question 10

Ahmad placed two test tubes with water of different temperatures in basins of water as shown below. What are the possible temperatures of the water in test tubes X and Y after ten minutes?

Accepted Answer

2. X: 30 °C, Y: 25 °C. Heat flows from hotter to cooler until both reach the same temperature, but not beyond. For test tube X in 30 °C water, the water inside X (originally cooler — the surrounding basin is at 30 °C) will gain heat from the basin and rise toward 30 °C, but cannot exceed 30 °C. For test tube Y in 15 °C water (originally hotter at some value), it will lose heat to the basin and fall toward 15 °C but cannot drop below 15 °C. Option (2) (X = 30 °C, Y = 25 °C) fits: X reaches the basin temperature of 30 °C, and Y cools toward 15 °C ending at 25 °C, both within their physically possible ranges.

P4 Science CA2 2021 — Catholic High

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