Topic 3- Waves Flashcards by Zarbanu Malekshahi

What are the two types of waves?

Transverse and longitudinal.

How well did you know this?

Not at all

Perfectly

What are the properties of a transverse wave? Give examples

Vibrations (oscillations) are perpendicular to the direction of travel. E.g. Light and electromagnetic waves.

How well did you know this?

Not at all

Perfectly

What are the properties of a longitudinal wave? Give examples

Vibrations (oscillations) are parallel to the direction of travel. E.g. Sound, ultrasound and earthquakes.

How well did you know this?

Not at all

Perfectly

What is amplitude?

The height of the wave from rest to crest, or rest to trough.

How well did you know this?

Not at all

Perfectly

What is frequency?

The number of complete waves in one second.

How well did you know this?

Not at all

Perfectly

What is the wavelength of a wave?

The distance between peak to peak, or trough to trough.

How well did you know this?

Not at all

Perfectly

What is the time period of a wave?

The time taken for a complete wave to pass a point.

How well did you know this?

Not at all

Perfectly

What do waves transfer?

Waves transfer energy and information without transferring matter.

How well did you know this?

Not at all

Perfectly

What is the equation for wave speed?

Frequency X wavelength.

How well did you know this?

Not at all

Perfectly

What is the equation for frequency?

1/time period.

How well did you know this?

Not at all

Perfectly

What can happen to a wave when it passes an edge?

It can be detracted.

How well did you know this?

Not at all

Perfectly

What does the extent of diffraction depend on?

The size of the size of the wavelength and gap. If they are more or less the same, then diffraction is maximum.

How well did you know this?

Not at all

Perfectly

What is the electromagnetic spectrum?

A range of different frequency waves. All waves travel at the same speed when they are in a vacuum and are all transverse.

How well did you know this?

Not at all

Perfectly

Give the order of the electromagnetic spectrum in terms of increasing frequency and decreasing wavelength

Radio waves
Microwaves
Infrared waves
Visible light 
Ultraviolet 
X-Rays
Gamma rays.

How well did you know this?

Not at all

Perfectly

What are the uses of radio waves?

Broadcasting and communications. The vibrations carry sound.

How well did you know this?

Not at all

Perfectly

What are the uses of microwaves?

Heating and satellite transmissions. The vibrations create heat.

How well did you know this?

Not at all

Perfectly

What are the uses of infrared waves?

Heating and night vision equipment. The vibrations create heat and cameras can detect this.

What are the uses of visible light waves?

Photography and optical fibres. Light can be reflected onto film or pass down tubes.

What are the uses of x-Ray’s?

Observing internal body structures. They waves pass through body tissues but get reflected off by our bones.

What are the uses of gamma rays?

sterilising medical equipment and food.

What are the dangers of microwaves?

Internal hearing of body tissues.

What are the dangers of infrared?

Causes skin burns and cell death.

What are the dangers of ultraviolet rays?

Damage to skin surface cells and can cause blindness.

What are the dangers of gamma rays?

Can cause cancer due to mutation in the cell’s DNA.

Describe an experiment to show that light refracts.

1) place a glass block and draw around its outline. 2) draw a normal and shine a light through it at a marked point. 3) mark where the ray leaves the block and draw the refractive wave. Repeated for different objects.

Equation for refractive index

Refractive index= sin(I) divided by sin(r)

How do you find the refractive index of a material such as glass?

Draw around a glass block and then shine a ray of light through it at a marked point. Mark where the Ray leaves the glass block and then draw in the refracted ray. Measure the angle of incidence and the angle of refraction and divide them to get n- the refractive index.

What is total internal reflection and when does it happen?

TIR takes place when the angle of incidence is greater than the critical angle. This means that no light leaves the medium.

What do we use TIR for?

We use them in SLR cameras to see the picture you're about to take and in optical fibres.

As light enters another medium it refracts. Why does light refract?

Because of the change in density in th two mediums.

Equation for sin(c)

1 divided by n (refractive index).

What are the characteristics of an analogue signal?

The amplitude and/or frequency varies.

What are the characteristics of a digital signal?

It is binary. The signal can only have 2 values, e,g, on or off.

What are the advantages of using digital signals over analogue?

- Analogue signals lose quality as they pick up interference but digital signals are either on or off so the signal remains high quality. - In analogue, signals of similar frequency cannot be sent along the same wire due to the interference it causes but this can be done with digital signals. (multiplexing) - When you round values, analogue signals lose a lot of information but digital signals do not. (Quantisation)

How can digital signals carry more information?

When digital signals are quantised, you can pack more information in as they on,y have two values (on or off)

Sound waves are longitudinal. What can happen to them?

- Reflected by hard, flat surfaces. - Refracted by different media as they speed up/slow down. - Diffracted through gaps and obstacles.

What is the frequency range for humans?

20Hz to 20,000Hz

Describe an experiment to measure the speed of sound in air

1) stand 100m away from a friend with ua stop watch. 2) make a noticeable sound (e.g. Crash cymbals) 3) get your friend to start the stop watch when you make the sound and to stop it when the sound reaches you. 4) divide the distance by the time taken= speed.

How can an oscilloscope be used to display a sound?

A microphone detects the sounds waves and feeds the information into an oscilloscope. The oscilloscope displays they sound as a wave.

How can you determine the frequency of a sound wave from an oscilloscope.

Make sure the X axis is time period and measure how long it takes for one come,eye cycle to take place. Frequency= 1/time period.

What is the pitch of a sound related to?

The frequency or vibration. If a wave vibrates a lot, it has a high frequency. If it has a high frequency, it has a high pitch.

What is the loudness of a sound related to?

The amplitude of the vibration. The bigger the vibration, the higher the amplitude. The higher the amplitude, the louder the sound.