Chapter 9: Waves and Light

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# Chapter 9: Waves and Light - PowerPoint PPT Presentation

Chapter 9: Waves and Light. 9.1: Waves of the E lectromagnetic Spectrum. As you sit and read your book, you are surrounded by waves from the sun that you cannot see or hear. These are electromagnetic waves

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### Chapter 9: Waves and Light

9.1: Waves of the Electromagnetic Spectrum
• As you sit and read your book, you are surrounded by waves from the sun that you cannot see or hear. These are electromagnetic waves
• Electromagnetic wave is a disturbance that involves the transfer or electric and magnetic energy

An electromagnetic wave is made up of vibrating electric and magnetic fields that move through space or some medium at the speed of light

The energy that the electromagnetic wave transfers through matter or space is called electromagnetic radiation

How do Electromagntic Waves Compare?
• All electromagnetic waves travel at the same speed in a vacuum, but they have different wavelengths and different frequencies

Wavelength: Distance between crest of one wave and the crest of the next wave

• Frequency of a wave: the number of waves that pass a given point in a certain amount of time.
• The higher the frequency, the smaller the wavelength and vice versa
What Makes up the Electromagnetic Spectrum
• The electromagnetic spectrum is made up of radio waves, microwaves, infrared rays, visible light, ultraviolet rays, X-rays, and gamma rays.
Electromagnetic Spectrum
• Radio waves: Longest Wavelengths, Shortest Frequencies
• Microwaves: have shorter wavelengths and higher frequencies than radio waves
• Infrared Rays: wavelengths shorter than microwaves, higher frequency and therefore more energy
Electromagnetic Spectrum
• Visible Light: electromagnetic rays that you can see (rainbow)
• Ultraviolet Rays: wavelengths shorter than visible light (helps produce vitamin D)
• X-rays: shorter wavelengths higher frequencies, more energy (penetrates most matter, bones absorbs it)
• Gamma Rays: Shortest wavelength and highest frequency, highest energy

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9.2: Reflection and Mirrors
• Why do you see your reflection in a mirror but not in a book?
• It all deals with how light reflects.
• Two ways in which a surface reflects light are regular reflection and diffuse reflection

All light rays reflect at the same angle

This will permit you to see a clear image

Diffuse reflection occurs when parallel rays of light hit an uneven surface.

Each light ray hits the surface at different angles because the surface is uneven

This causes the image to be blurry or not seen

What type of Images do Mirrors Produce?

Plane Mirror: flat sheet of glass

This type of mirror produces a virtual image. So it’s an image that doesn’t exist.

Your image appears to be behind the mirror

The virtual image is upright and the same size of the object

Have you ever looked at yourself in curved mirrors at a fun house?

Concave Mirrors
• This type of mirror curves inward like the inside of a bowl
• The light is being reflected parallel to the optical axis, which is an imaginary line that divides the mirror in half
• The point at which all rays meet is the focal point
• Concave mirrors produce real or virtual images

If the object is farther away from the mirror than the focal point, the reflected rays forms a real image

A real image can be projected on a piece of paper, and can be larger or smaller than the object they are also upside down

If an object is between the mirror and the focal point, the reflected rays form a virtual image

Convex Mirrors

Convex mirrors curve outwards

A convex mirror produces a virtual image that is always smaller than the object

9.3: Refraction and Lenses

When light hits an object, it can be reflected, refracted and /or absorbed

Optical Illusion In a Fish Tank

There is only one fish in

the tank, but refraction

makes it look

as though there are two.

• An opaque object will reflect and absorb light.
• The more transparent an object is, the less light it will absorb
Refraction in Different Mediums

Refraction of Light

The light ray bends

as it passes through different mediums.

• Some mediums cause light to bend more than others
• Light travel fastest in in air
• To know how much light bends we measure the index of refraction
• The higher the index of refraction, the more light bends
Prisms and Rainbows

When white light enters s prism, each wavelength is refracted by different amount

The longer the wavelength and less the wave is bent.

Water + Light= Rainbow

What Determines the Type of Image Formed by a Lens?

When you look through binoculars, a camera or eyeglasses you are using lens to bend light

A lens is a curved piece of glass or other transparent material that refracts light

The type of image formed by a lens depends on the shape of the lens and the position of the object

Concave Lens

A concave lens produces a virtual image that is upright and smaller than the object

How a Convex Lens Works

The type of image formed by a convex lens depends on the object’s position.

The Changing Speed of Sound

Sound travels faster through steel than air, even though steel is denser, because steel is also less compressible