topic 4

Question 1

sonar is an example of a use of ultrasound

state one other example of a use of ultrasound

Answer 1

foetal scanning

Question 2

state an example of a use of infrasound

Answer 2

studying the earths structure

Question 3

students measuring speed of sound in air

explain one way these students could improve their method

Answer 3

use a datalogger (to start and stop time) to give a more measureable time

Question 4

describe how hitting the rod causes a sound wave to travel along the inside of the rod

Answer 4

particles at the end vibrate more causing neighbouring particles to vibrate

Question 5

describe how the student could measure the angle of refraction

Answer 5

mark where the ray went into and out of the block. remove block and join entry and exit points

Question 6

explain what happens to radio waves after they meet the boundary between the lower and upper layers shown in figure 6

Answer 6

wave P refracts towards the normal because P slows down. wave Q is reflected (at equal angle from boundary) without a change in speed

Question 7

explain why their reaction times vary so much

Answer 7

the reaction time will be different for each of the students because the students are at different distances

Question 8

explain one way students might improve the experiment to measure speed of sound in air

Answer 8

use an electronic timer to eliminate reaction time

Question 9

describe two differences between the hearing responses of the human and the mouse

Answer 9

1. mice is more sensitive to higher frequencies

2. humans have a lower intensity of sound to just hear

Question 10

a farmer wants to scare away birds state which frequency will be most effective

state the reason for your choice

Answer 10

2.5kHz

frequency corresponds with most sensitive

Question 11

describe the difference between ultra and infrasound

Answer 11

infrasound below 20Hz whereas ultrasound is above 20,000Hz

Question 12

explain how vibrations from earthquakes may be used to study the core of the earth

Answer 12

use of seismometers which can show different densities as waves can be refracted in the interior of the earth. some seismic waves are longitudinal and some are transverse

Question 13

figure 8 represents a sound wave coming from a loudspeaker and shows the effect on particles of the air at one instant in time

describe the motion of the particles as the wave travels through air

Answer 13

particles vibrate about fixed positions

Question 14

calculate depth of water when waves travel at 1500m/s and time is 48 milliseconds

Answer 14

d = 1/2v x t

= 1/2 5000 x 0.048

= 36

Question 15

describe how the vibrating tuning fork causes a sound wave to travel through the air

Answer 15

the prong makes the air vibrate in the same direction the wave travels

Question 16

speed of light = 3.0 x 10^8 m/s
wavelength of yellow light = 5.8 x 10^-7m

use frequency = speed / wavelength to calculate frequency of yellow light state units

Answer 16

3.0 x 10^8 / 5.8 x 10^-7

= 5.2 x 10^14 Hz

Question 17

which colour of visible light has the longest wavelength?

A) blue
B) green
C) red
D) yellow

Answer 17

C) red

Question 18

explain why an infrared remote control may not switch the TV from behind an armchair on but a radio wave control always will

Answer 18

radio waves can go though objects as infra red and radio have different wavelengths

Question 19

which is a converging lens with greatest power?

A
B
C
D

Answer 19

B