CIE iGCSE Co-Ordinated Science P3.3 Electromagnetic spectrum Exam Style Questions Paper 3
Question
A person climbs a mountain.
(a) The person is exposed to infrared and ultraviolet radiation from the Sun.
Infrared and ultraviolet radiation are part of the electromagnetic spectrum.
(i) Fig. 3.1 shows an incomplete electromagnetic spectrum.
On Fig. 3.1, write infrared and ultraviolet in their correct places.
(ii) Ultraviolet waves travel at 300 000 000 m / s in a vacuum.
State the speed of infrared waves in a vacuum.
(b) The person makes a loud sound and then hears an echo.
State what is meant by an echo.
(c) The person takes a photograph with a camera.
The camera contains a thin converging lens.
Fig. 3.2 shows an incomplete ray diagram for a thin converging lens forming an image.
(i) State the name of the points labelled F on Fig. 3.2.
(ii) On Fig. 3.2:
• draw a line to complete the path of ray 2
• draw the image formed
• label the image.
(d) The person drops the camera from the top of the mountain. The camera falls down the mountain.
Fig. 3.3 shows the distance–time graph for the motion of the camera over the first 6.0 s
Use Fig. 3.3 to determine the average speed of the camera over 6.0 s.
▶️Answer/Explanation
Ans : 3(a)(i)
infrared correct ;
ultraviolet correct ;
3(a)(ii) 300 000 000 (m / s) ;
3(b) the reflection of sound ;
3(c)(i) principal focus / focal point ;
3(c)(ii) horizontal line drawn from lens to intersect with ray 1 ;
inverted (labelled) arrow for image ;
3(d) total distance 180m ;
evidence of speed = distance ÷ time / 180 ÷ 6.0 ;
30 (m/ s) ;
Question
(a) The mass of the Sun is 1.97 × 1030 kg.
The average density of the Sun is 1410 kg / m3.
Calculate the volume of the Sun.
volume = ……………………………………………. m3
(b) The Sun is made of very hot gas.
(i) Suggest the main method of thermal energy transfer from the inside of the Sun to the surface of the Sun.
(ii) State the main method of energy transfer that occurs when infrared waves travel from
the Sun to the Earth through space.
(iii) Sound energy is produced by the Sun.
Explain why we are unable to hear this sound on Earth.
(c) (i) Fig. 12.1 shows an incomplete electromagnetic spectrum.
Write infrared radiation in its correct place.
(ii) State the electromagnetic radiation which has the highest frequency.
(iii) Explain why it takes the same time for infrared and visible light to travel from the Sun to
the Earth.
(d) Fig. 12.2 shows a sound wave.
(i) On Fig. 12.2, label the amplitude of the wave with a double-headed arrow (↔) or (↕) and the letter A.
(ii) On Fig. 12.2, label the wavelength of one wave with a double-headed arrow (↔) or (↕) and the letter W.
▶️Answer/Explanation
Ans : 12(a) volume = mass/density (in any form) or 1.97 × 1030 / 1410 ;
= 1.4 × 1027 (m3) ;
12(b)(i) convection ;
12(b)(ii) radiation ;
12(b)(iii) sound waves need a medium / cannot travel through a vacuum ;
12(c)(i) infrared to the right of visible light ;
12(c)(ii)gamma radiation ;
12(c)(iii) all electromagnetic waves / they travel at same speed ;
12(d)(i) amplitude correctly labelled ;
12(d)(ii) wavelength correctly labelled ;
Question
(a) A spacecraft carrying an astronaut travels 384 000 km from the Earth to the Moon in 78 hours.
Calculate the average speed of the spacecraft in km / s.
average speed = ………………………………………… km / s
(b) The mass of the astronaut on the Earth is 90 kg.
(i) Calculate the weight of the astronaut on the Earth.
The gravitational force on unit mass, g, is 10 N / kg.
weight = …………………………………………….. N
(ii) State the mass of the astronaut on the Moon.
mass = ……………………………………………. kg
(c) (i) The astronaut communicates with Earth using radio waves.
Fig. 3.1 shows an incomplete electromagnetic spectrum.
Write radio waves in the correct position in Fig. 3.1.
(ii) Explain why it is not possible for the astronaut to communicate with Earth using sound waves.
(d) The astronaut collects a lump of moon rock.
The rock contains iron-60, a radioactive isotope.
(i) State the meaning of the term isotope.
(ii) Iron-60 decays by the emission of β-particles.
Complete the sentences to describe the nature of β-particles.
β-particles are identical in nature to ………………………………… .
β-particles have a single ………………………………… charge.
▶️Answer/Explanation
Ans : 3(a) 78 hours = 78 × 3600 = 280 800 seconds ;
speed = distance / time (in any form) or 384 000 / 280 800 ;
= 1.37 (km / s) ;
3(b)(i) weight = mass × g (in any form) or 90 × 10 ;
= 900 (N) ;
3(b)(ii) 90 (kg) ;
3(c)(i) radio (waves) in right hand box ;
3(c)(ii) sound waves need a medium / sound waves do not travel through a vacuum ;
3(d)(i) atoms of the same element that have different numbers of neutrons ;
OR
atoms which have the same number of protons and different numbers of neutrons ;
OR
atoms which have the same atomic number but different mass number ;
3(d)(ii) electrons ;
negative ;
Question
(a) High frequency sound waves are called ultrasound.
An ultrasound wave travels 13.5cm in 0.000090s through water.
Calculate the speed of the ultrasound wave in m/s.
speed = …………………………………………. m/s
(b) Ultrasound waves are used in hospitals to scan unborn babies.
(i) Suggest a reason why it is not safe to scan unborn babies with X-rays.
(ii) State one use for X-rays in a hospital.
(c) (i) γ-radiation is used in hospitals to kill cancerous cells.
Fig. 3.1 shows an incomplete electromagnetic spectrum.
Write γ-radiation in its correct place.
(ii) A source of γ-radiation in a hospital is technetium-99.
Technetium-99 has a half-life of 6 hours.
The source contains 1280 undecayed atoms.
Calculate how many atoms will have decayed after 12 hours.
number of decayed atoms = …………………………………………………
▶️Answer/Explanation
Ans : 3(a) evidence of 13.5 cm = 0.135 m ;
evidence of speed = distance / time (in any form) or 0.135 / 0.000090;
= 1500 (m / s) ;
3(b)(i) ionising radiation damages / kills human cells or damages DNA ;
3(b)(ii) observing broken bones etc ;
3(c)(i) ϒ – radiation on left hand side ;
3(c)(ii) 2 half lives ; (320 remain so ) 960 atoms decayed ;
Question
Bats use the reflection of sound waves to determine the position of objects.
Fig. 6.1 shows a bat, and a moth flying in front of the bat.
(a) State the name given to a reflected sound wave. (Topic – P3.4)
▶️Answer/Explanation
Echo
Explanation: An echo is the reflection of sound waves off a surface, which is how bats detect objects in their environment.
(b) Some bats are able to detect ultraviolet radiation. Ultraviolet radiation is part of the electromagnetic spectrum. (Topic – P3.3)
(i) On the incomplete electromagnetic spectrum shown in Fig. 6.2, place ultraviolet in the correct position.
▶️Answer/Explanation
Ultraviolet should be placed between X-rays and infrared.
Explanation: The electromagnetic spectrum is ordered by wavelength and frequency. Ultraviolet (UV) radiation has a shorter wavelength and higher frequency than visible light but longer wavelength and lower frequency than X-rays.
(ii) State which part of the electromagnetic spectrum has the lowest frequency.
▶️Answer/Explanation
Radio waves
Explanation: Radio waves have the longest wavelength and the lowest frequency in the electromagnetic spectrum.
(c) A bat produces a sound wave with a frequency of 200 kHz and a wavelength of 0.0016 m.
(i) Draw straight lines to link each wave term to its definition. (Topic – P3.1)
▶️Answer/Explanation
Amplitude – Maximum displacement of points on a wave
Frequency – Number of waves passing a fixed point per second
Wavelength – Distance between the peaks on consecutive waves
Explanation: Amplitude is the height of the wave, frequency is how often the wave passes a point, and wavelength is the distance between two consecutive peaks or troughs.
(ii) Explain why a human cannot hear the sound emitted by the bat. (Topic – P3.4)
▶️Answer/Explanation
Humans cannot hear sounds with frequencies above 20 kHz.
Explanation: The human hearing range is typically between 20 Hz and 20 kHz. The bat’s sound wave has a frequency of 200 kHz, which is well above the upper limit of human hearing.
(iii) The bat changes the frequency of the sound it produces from 200 kHz to 250 kHz. State what happens to the pitch of the sound. (Topic – P3.4)
▶️Answer/Explanation
The pitch increases.
Explanation: Pitch is directly related to frequency. As the frequency increases from 200 kHz to 250 kHz, the pitch of the sound also increases.
Question
(a) Fig. 9.1 shows a rocket about to be launched.
(i) The weight of the rocket is 8000000N.
When the rocket is launched, the upward force exerted by the rocket is 12000000N.
Calculate the resultant upward force on the rocket.
resultant force = …………………………………………….. N
(ii) Explain why the resultant force cannot be zero, when the rocket is launched.
………………………………………………………………………………………………………………………….
………………………………………………………………………………………………………………………….
(iii) The rocket travels 385000km from the Earth to the Moon in 75 hours.
Calculate the average speed of the rocket in km/ s.
speed = ………………………………………… km/s
(b) An astronaut on the rocket uses a telescope to view a star.
Fig. 9.2 shows a lens that is used in the telescope. Light rays from the star pass through the
lens and are focused at the principal focus.
(i) On Fig. 9.2, label the principal focus of the lens with the letter F.
(ii) On Fig. 9.2, draw a double headed arrow ( ↔ ) to indicate the focal length of the lens.
(iii) State the name of the process that occurs when light passes into the lens and the direction of the light changes.
…………………………………………………………………………………………………………………….
(c) The astronaut communicates with Earth using radio waves.
(i) Place radio waves in the correct place in the incomplete electromagnetic spectrum shown in Fig. 9.3.
Fig. 9.3
(ii) State which part of the electromagnetic spectrum has the greatest frequency.
…………………………………………………………………………………………………………………….
(iii) Explain why it is not possible for the astronaut to use sound waves to communicate directly with Earth.
…………………………………………………………………………………………………………………….
…………………………………………………………………………………………………………………….
▶️Answer/Explanation
Ans: 9(a)(i) 4 000 000 (N) ;
9(a)(ii) rocket would not, move/take off ;
9(a)(iii) conversion of 75 hours to seconds / 270 000 s ;
speed = distance ÷ time or substituted distance ÷ time ;
speed = 1.43 (km/s) ;
9(b)(i) principal focus correctly identified ;
9(b)(ii) focal length correctly identified ;
9(b)(iii) refraction ;
9(c)(i)
9(c)(ii) $\gamma$- rays ;
9(c)(iii) there is no medium / there is a vacuum ;
no particles to transfer the vibrations (preventing sound from travelling) ;
Question
(a) A person standing on a warm, sunny beach is exposed to several forms of electromagnetic radiation.
Fig. 12.1 shows part of the electromagnetic spectrum.
Complete Fig. 12.1 by writing the names of the other two forms of electromagnetic radiation in the correct places.
(b) The person stands with both feet on some very soft sand on the beach.
When one foot is lifted off the sand, the other foot sinks deeper into the sand.
Explain why this happens.
…………………………………………………………………………………………………………………………………
…………………………………………………………………………………………………………………………………
(c) A sample of sand has a mass of 8000kg.
This sand has a density of 1600kg/m$^{3}$.
(i) Calculate the volume of this sample of sand.
volume = …………………………………. m$^{3}$
(ii) Show that the weight of this sample of sand is 80000N.
The gravitational field strength, g, is 10N/kg.
(d) A piece of glass has been left on the beach. The glass acts like a convex lens focusing the Sun’s rays.
Fig. 12.2 shows two rays of light passing through a convex lens.
(i) Complete the light rays in Fig. 12.2 to show how the light rays are focused by the lens.
(ii) State the name of point F.
…………………………………………………………………………………………………………………….
(iii) On Fig. 12.2, draw a double headed arrow (↔) to indicate the focal length of the lens.
▶️Answer/Explanation
Ans: 12(a)
microwaves in correct place ;
X-rays in correct place ;
12(b) area decreases ;
so pressure increases ;
12(c)(i) volume = mass / density (in any form symbols or words) or 8000 / 1600 ;
= 5 (m$^{3}$ ) ;
12(c)(ii) 8000 × 10 ;
(= 80 000 N)
12(d)(i) rays meet at focus (F) ;
Question
3. (a) (i) State which wave in the electromagnetic spectrum has the highest frequency.
▶️Answer/Explanation
Answer: γ-ray
Sub-topic Code: P5.1 (Electromagnetic Spectrum)
Detailed Solution: Gamma rays (γ-rays) have the highest frequency in the electromagnetic spectrum, making them the most energetic type of electromagnetic radiation.
3. (a) (ii) State which wave is emitted by a remote control for a television.
▶️Answer/Explanation
Answer: infrared
Sub-topic Code: P5.1 (Electromagnetic Spectrum)
Detailed Solution: Remote controls for televisions emit infrared waves, which are used to send signals to the TV.
3. (b) (i) State the effect shown by the ray of light at B in Fig. 3.1.
▶️Answer/Explanation
Answer: refraction
Sub-topic Code: P6.1 (Light)
Detailed Solution: The ray of light at B undergoes refraction, which is the bending of light as it passes from one medium (air) to another (glass).
3. (b) (ii) State the name of the line labelled PQ in Fig. 3.1.
▶️Answer/Explanation
Answer: normal
Sub-topic Code: P6.1 (Light)
Detailed Solution: The line labelled PQ is called the normal, which is an imaginary line perpendicular to the surface at the point where the light ray enters the glass block.
3. (b) (iii) State the value of angle x in Fig. 3.1.
▶️Answer/Explanation
Answer: 45°
Sub-topic Code: P6.1 (Light)
Detailed Solution: Angle x is the angle of refraction, which is given as 45° in the diagram.
3. (b) (iv) The glass block in Fig. 3.1 is resting on a bench. The glass block exerts a pressure on the bench. State the two variables that must be measured to determine the pressure exerted.
▶️Answer/Explanation
Answer: force / mass / weight; area
Sub-topic Code: P2.1 (Forces)
Detailed Solution: To calculate pressure, you need to measure the force (or weight) exerted by the glass block and the area of contact between the block and the bench. Pressure is calculated as force divided by area.
3. (b) (v) The mass of the glass block is 156 g. The volume of the glass block is 60.0 cm³. Calculate the density of the glass block.
▶️Answer/Explanation
Answer: 2.60 g/cm³
Sub-topic Code: P4.1 (Density)
Detailed Solution: Density is calculated as mass divided by volume. For the glass block, density = 156 g / 60.0 cm³ = 2.60 g/cm³.
3. (c) (i) Place α-particles, β-particles, and γ-rays in order of their ionising ability.
▶️Answer/Explanation
Answer: α, β, γ
Sub-topic Code: P12.1 (Radioactivity)
Detailed Solution: α-particles have the highest ionising ability, followed by β-particles, and γ-rays have the least ionising ability.
3. (c) (ii) State which one of these radiations is negatively charged.
▶️Answer/Explanation
Answer: β
Sub-topic Code: P12.1 (Radioactivity)
Detailed Solution: β-particles are negatively charged, as they are high-energy electrons.
3. (c) (iii) State which one of these radiations is the most penetrating.
▶️Answer/Explanation
Answer: γ
Sub-topic Code: P12.1 (Radioactivity)
Detailed Solution: γ-rays are the most penetrating type of radiation, as they can pass through most materials, including thick layers of concrete or lead.