WAVES

All waves carry energy from one point to another without transferring matter. As an example, when sound travels through air the air molecules don’t actually travel all the way from the point of origin of the sound to the point where it is heard by an individual. The atoms only vibrate back and forth transferring mechanical energy. Can sound travel in a vacuum? N0! If there aren’t any air molecules there is nothing present in which the energy can be transferred. Properties of Waves

Waves are categorized as either transverse or longitudinal Waves are categorized as either transverse or longitudinal. In the case of longitudinal waves the matter vibrates parallel to the direction of energy movement. In the case of transverse waves, the matter vibrates perpendicular (at right angles to) the direction of energy flow. Sound is an example of a longitudinal wave. An ocean wave is an example of a type of transverse wave. All electromagnetic waves are transverse waves. Types of Waves:

Electromagnetic Waves: If all electromagnetic waves are transverse waves then how do X-rays differ from red light? To understand this you must be familiar with terms regarding waves. Wavelength: is the distance from a given point on a wave to the next similar point on the wave. This is usually measured from peak to the next similar peak. Speed: this is the speed at which the wave travels Frequency: is the number of wave crests which pass by each second Amplitude: is the distance from the center-line of the wave to the top of the peak. Electromagnetic Waves:

Note how the characteristics of waves relates to the wave below. Wavelength Amplitude Note how the characteristics of waves relates to the wave below.

As the wavelength of a wave decreases, how is the frequency effected? If the speed of the wave remains the same while the wavelength is shortened, the number of crests passing by per second would increase. This is the major reason why waves of the same type differ from one another. As an example, not all sound is at the same pitch. All sound travels at the same speed but due to different wavelengths, the waves have different frequencies. Frequency determines pitch. The higher the frequency the higher the pitch. Blue light has a shorter wavelength than red light. X-rays have shorter wavelengths than visible light. As the wavelength of a wave decreases, how is the frequency effected?

If you were to change the amplitude of a wave would this effect the other properties of the wave? No, the amplitude would not effect the speed, or the wavelength. The main characteristic which would be altered is the volume. A sound wave with large amplitude is “Loud”. A light wave with large amplitude is “Bright”.

What type of wave?? X-Ray Transverse Longitudinal Sound Wave Blue Light Radio Waves What type of wave??

Which property of a wave determines the following for sound? Volume Amplitude Wavelength Pitch

The Doppler effect is the change in the perceived pitch of sound due to either the motion of the observer or the sound generator. Anytime an object making sound is moving towards you, you will perceive the pitch of the sound at a higher frequency than it is actually being produced. The Doppler Effect

EXAMPLE: A frequency of 256 Hz is middle C on a musical scale EXAMPLE: A frequency of 256 Hz is middle C on a musical scale. If a car is honking its horn, which is producing a frequency of middle C, and at the same time driving towards you, you will actually hear this sound at a higher frequency (pitch). The Doppler Effect

The Doppler Effect EXAMPLE: Car honking its horn If the car is moving away from you, you will perceive the pitch of the horn at a lower frequency than it is actually being generated. This is also true (lower frequency) if you the observer are moving and the sound generator is at rest. If you are moving towards the car you will hear the pitch of the horn at a higher frequency. If you are moving away from the stationary car you will hear the pitch of the horn at a lower frequency. The Doppler Effect

In general, you measure the relative motion between two objects to determine if the pitch would be higher or lower. If the relative motion is “moving away from each other” , the pitch will be lower. If the relative motion is “moving closer together”, the pitch will be higher. The Doppler Effect

Determine whether the objects would hear the sound at a frequency higher or lower than it is being generated. Van hears sound of sports car at Higher pitch Lower pitch Higher Pitch Sports car hears sound of Fire Engine Fire engine hears sound of sports car at Sports Car hears sound of jet at Jet hears sound of Sports Car at Speed = 400mi/hr Speed = 35mi/hr Speed = 35mi/hr Speed = 60mi/hr