Waves

Question 1

What is a Transverse Wave?

Answer 1

> Particles within the wave move perpendicular to the direction

Question 2

Give examples of Transverse waves?

Answer 2

> E.M. Waves, Water waves, Light waves

Question 3

What is a Longitudinal wave?

Answer 3

> Particles oscillate in the same direction (parallel) as the wave movement.

Question 4

Give Examples of Longitudinal Wave?

Answer 4

> Seismic Waves, Sound Waves

Question 5

What is Wavelength?

Answer 5

> Distance from one point to another.

Question 6

What is the Frequency?

Answer 6

> Number of waves/second

Question 7

What is a period?

Answer 7

> Time taken to produce one wave.

Question 8

How do you workout the Wave Speed?

Answer 8

Wave speed = Frequency X Wavelength
(M/s) (M) (Hz)

Question 9

Explain how to carry out the Ripple tank experiment?

Answer 9

1)Set up the ripple tank as shown in the diagram with about 5 cm depth of water.
2)Adjust the height of the wooden rod so that it just touches the surface of the water.
3)Switch on the lamp and motor and adjust until low frequency waves can be clearly observed.
4)Measure the length of a number of waves then divide by the number of waves to record wavelength. It may be more practical to take a photograph of the card with the ruler and take measurements from the still picture.
5)Count the number of waves passing a point in ten seconds then divide by ten to record frequency.
6)Calculate the speed of the waves using: wave speed = frequency × wavelength.

Question 10

Explain How to carry out the Waves in A solid Practical?

Answer 10

1)Attach a string or cord to a vibration generator and use a 200 gram (g) hanging mass and pulley to pull the string taut as shown in the diagram. Place a wooden bridge under the string near the pulley.

2)Switch on the vibration generator and adjust the wooden bridge until stationary waves can be clearly observed.

3)Count the number of loops. Divide the length of the oscillating part of the string by this number of loops to get the length of one loop. The length of each loop is half a wavelength, so double this to get the length of one wavelength.

4)The frequency is the frequency of the power supply.

5)Calculate the speed of the waves using: wave speed = frequency × wavelength.

Question 11

How to Measure the speed of sound?

Answer 11

1)Set up the oscilloscope so the detected waves at each microphone are shown as separate waves.
2)Start with both microphones next to the speaker, then slowly move on away until the two waves are aligned on display.
3)Measure the distance between the microphone to find one wavelength.

Question 12

What are Electro Magnetic Waves?

Answer 12

> All E.M. waves are transverse waves that transfer energy from a source to an absorber
All E.M. waves travel at the same speed through air or a vacuum.

Question 13

Name all the E.M. waves in the spectrum in order?

Answer 13

> Radio Waves
Microwaves
Infrared
Visible Light
U.V.
X-rays
Gamma

Question 14

How are Radio waves used with their Properties?

Answer 14

> They are about 10cm
used for communication e.g. radio and TV
They are transmitted easily through air.
They don’t cause damage to human body, they an be reflected to change their direction.

Question 15

How are Micro waves used with their Properties?

Answer 15

> Used for cooking food and Satellite communications
High frequency microwaves have frequencies which are easily absorbed by molecules in food.
The internal energy of the molecules increases when they absorb microwaves which causes heating

> They pass easily through the atmospheres they can pass between stations on Earth and satellites in orbit.

Question 16

How is Infrared used with their Properties?

Answer 16

> Used for electrical heaters, cooking food, cameras.
The infrared has frequencies which are absorbed by some chemicals bonds
The internal energy of the bonds increases when they absorb infrared light=heating.

Question 17

How is visible light used with their Properties?

Answer 17

> Fibre Optic Communicator, light we can see
They work because of reflection, the light rays are bounced and forth until they reach the end of the fibre
.Light is not easily absorbed or scattered as it travels along a fibre.

Question 18

How are U.V Light used with their Properties?

Answer 18

> Used for energy efficient lamps, sun tanning.
Has hazardous effects on human body

> Fluorescent substances are used in energy-efficient lamps, they absorb UV light produces inside the lamp and re-emit the energy as visible light.

Question 19

How are X-Rays and Gamma rays used with their Properties?

Answer 19

> Used for Medical imaging and treatments.
X-rays pass easily through flesh but not so easily through denser material.
Radiographers use X-rays and gamma rays to treat people with cancer.
Gamma radiation can be used as a medical tracer
It is well suited it can pass through the body to be detected

Question 20

How can E.M. Waves be dangerous?

Answer 20

> UV waves can cause human skin to age earlier than expected. They are in between light and X rays in the electromagnetic spectrum and they can also cause skin cancer. UV waves can also be harmful to human eyes.
Similar to UV rays, X rays and gamma rays can also have harmful effects on human skin. In fact, X rays and gamma rays will increase the risk of cells mutating and dividing uncontrollably, which can potentially lead to skin cancer.

Question 21

How do you measure the risk?

Answer 21

> Sieverts are the units of the radiation. The symbol for sievert is Sv. Like most other units, sieverts can come in different factors, such as millisieverts (mSv).
1000 millisieverts make up one sievert. Since background radiation is at such a low level, you will commonly see the unit mSV rather than the unit Sv.