Waves - Year 9 Science Notes + Practice

 

 

  1. ==Recall the definition of energy and the forms it can take.==

Energy is the ability to do work. It cannot be created or destroyed, however it can be stored. It is all around us. Forms of energy include mechanical energy, sound energy, nuclear energy, thermal energy, electrical energy, light energy and gravitational energy. These are all either kinetic energy or potential energy.

  1. ==Define the following terms:==

  2. Heat. Heat or “thermal energy” is a type of energy transfer in which heat is transferred from a warmer object to a cooler object.

  3. Convection. Convection is a type of heat transfer which occurs in fluids and gases. Take a house for example. Hot air is less dense than cool air, so hot air will rise to the top of the house. As the hot air gets further from the heat source, it will begin to become more dense and therefore fall downwards. This same process is what allows hot air balloons to fly.

  4. Conduction. Conduction is a type of heat transfer that happens when a hotter object comes into contact with a cooler object. Particles in hot objects vibrate faster than that of cooler objects. This means that when a hotter object touches a cooler one, the fast moving particles in the hot object will begin to nudge the cooler object’s slow moving particles. Soon, all of the particles will begin to vibrate faster in the cooler object until it reaches the same temperature as that of the once hotter object.

  5. Insulator. An insulator is a material that does not let heat pass through it easily. For example, rubber is an insulator whilst iron is not.

  6. Radiation. The emission of energy through waves or particles travelling through space or other media.

    1. ==Define the following terms:==
    2. Wavelength. The distance between two crests of a wave.
    3. Frequency. The number of waves that pass a specific point in a specified amount of time.
    4. Amplitude. The distance between the crest and rest of the wave.
    5. Speed. The distance travelled by a given point on the wave in a given interval of time.
    6. Hertz. The standard unit of frequency.
    7. Velocity. The product of the wave in question’s frequency and wavelength. Sometimes, velocity is used interchangeably with the term “speed''.

  7. Medium. A substance that makes the transferring of energy possible.

  8. ==Label the features of a transverse wave:==

 

  1. ==Label the features of a longitudinal wave:==

 

  1. ==Be able to apply the wave formula to problems:==

1. A wave with a frequency of 14 Hz has a wavelength of 3 meters. At what speed will this wave travel?

2. The speed of a wave is 65 m/sec. If the wavelength of the wave is 0.8 meters, what is the frequency of the wave?

 3. A wave has a frequency of 46 Hz and a wavelength of 1.7 meters. What is the speed of this wave?

4. A wave traveling at 230 m/sec has a wavelength of 2.1 meters. What is the frequency of this wave?

5. A wave with a frequency of 500 Hz is traveling at a speed of 200 m/s. What is the wavelength?

6. A wave has a frequency of 540 Hz and is travelling at 340 m/s. What is its wavelength?

7. A wave with a wavelength of 125 metres is moving at a speed of 20 m/s. What is its frequency?

 8. A wave has a frequency of 900 Hz and a wavelength of 200 m. At what speed is this wave travelling?

 9. A wave has a wavelength of 0.5 metres and a frequency of 120 Hz. What is the wave’s speed?

10. Radio waves travel at a speed of 300,000,000 m/s. WFNX broadcasts radio waves at a frequency of 101,700,000 Hertz. What is the wavelength of WFNX’s radio waves?

  1. ==What are sound waves and how do they transfer energy?==

Sound waves are a longitudinal wave. In sound waves, energy is transferred through vibration of air particles or particles of a solid through which the sound travels.

  1. ==Describe visible light as part of the electromagnetic spectrum and the applications of reflection, absorption, and refraction.==

Reflection. Reflection is light bouncing off a medium without absorbing it. Absorption. A process in which light is absorbed and converted into energy. Refraction. Refraction is the bending of light when it enters a medium that is denser or has a higher refractive index than the one it originated from.

  1. ==Describe real world applications of the electromagnetic spectrum.==

Radio waves are used in telecommunications. Infrared is used in tv remote controls. UV light can be used in tanning beds. X-Rays are used to produce medical imagery. Visible light is used to see. Microwaves are used for cooking.

Gamma rays can be used to treat cancer. Radio waves can be used in radio. Microwaves can be used for RADAR. Uv is used for discos.

  1. ==How is energy transferred via convection and conduction?==

Conduction is heat transfer via touching. The particles in the hotter object vibrate very fast as the temperature of the is high. The particles in the cooler object vibrate slower than those in the hotter object. As the two come into contact, the fast moving particles will begin to nudge the other particles until they start to vibrate fast too. This will transfer heat from the hotter object to the cooler object. Convection is the movement caused within a fluid by the tendency of hotter and therefore less dense material to rise, and colder, denser material to sink under the influence of gravity, which consequently results in transfer of heat.

 

 V = Velocity

L = Wavelength

F = Frequency

 

 

Electromagnetic Spectrum