Chapter. 27 Physics

What is the speed of light and how is it represented?

300,000 km/s. Represented at c.

The time it takes light to travel across the orbit of Earth is about?

8 minuets.

Penumbra

A partial shadow that appears where light from part of the source is blocked and light from another source is not blocked.

Shadow

A shaded region that results when light falls on an object and thus cannot reach into the region on the far side of the object.

Ray

A thin beam of light.

Electromagnetic Wave

A wave that is partly electric and partly magnetic and carries energy. Emitted by vibrating electric charges.

Translucent

Allowing light, but not dependable images to come through.

Most shadows are?

Blurry

Light is an energy that is given off by an accelerating electric ______.

Charge.

Just as a sound wave can force a sound receiver into vibration, a light wave can force ______ ________ in materials into vibrations.

Charged particles.

Who published a theory explaining the photon-electric effect?

Einstein.

Infrared

Electromagnetic eaves of frequencies lower than the red of visible light.

Ultraviolet

Electromagnetic waves of frequencies higher than those of violet light.

You can get a sunburn on a sunny day and on an overcast day. But, you cannot get a sunburn if you are behind a glass. Explain.

Glass does not let Ultraviolet light through, but clouds do.

Energy of motion is?

Heat

Who thought light was waves?

Huygens.

Your friend says that microwaves and ultraviolet light have different wavelengths but travel through space at same speed. Do you agree or disagree? Defend your answer.

I agree. With different wavelengths, there are different frequencies and periods as well.

Photon

In the particle model of electromagnetic radiation, a particle that travels only at the speed of light and whose energy is related to the frequency of the radiation in the wave model.

The extra vibrations of the electrons in the glass create ______ energy.

Kinetic.

What evidence can you cite to support the idea that light can travel through a vacuum?

Light from the sun travels through the vacuum of space.

Describe the 2-fold nature of light.

Light has a dual nature: Part particle (Photon), Part wave. Theory by Einstein.

Electromagnetic Spectrum goes from:

Low - high frequency. long - short wavelength. low - high energy. and they are all travel at the same speed.

Who thought light was particles?

Newton.

Will glass be transparent to light with frequencies that match its natural frequencies that match its own natural frequencies? Explain your answer.

No. Resonance would occur and energy is not re-emitted.

Solar Eclipse-

Occurs when moon is between earth and sun. It had to be day time to see and you have to be in the umbra.

Lunar Eclipse-

Occurs when the moon passes behind the Earth and goes through the earths shadow. Has to be night time to see it.

Most things wont let light pass through at all is?

Opaque .

Shadows have an area on the edges where some of the light is blocked called the?

Penumbra

Mass-less bundles of electromagnetic energy packed in bundles called what?

Photons.

Why do polarized sunglasses reduce glare, whereas unpolarized sunglasses simply cut down on the total amount of light reaching our eyes?

Polaroid sunglasses have vertically polarized lens which block the horizontally polarized glare.

Tell the Electromagnetic Spectrum in order.

Radio Microwaves Infrared Visible Light Ultraviolet X-rays Gamma Rays

A thin beam of light

Ray

Most of what we see today is what light?

Reflected.

Who calculated the speed of light to be 300,000 km/s?

Roemer.

The area around an object where the light rays do NOT reach is called a?

Shadow.

Your friend says that any radio wave travels faster than any sound wave. Do you agree or disagree and why?

Sound waves travel much slower than the speed light or any electromagnetic wave.

Suppose the sunlight is incident upon both a pair of reading glasses and a pair of sunglasses. Which pair would you expect to be warmer, and why?

Sunglasses, they will absorb more light.

Who showed that light could spread out like waves?

T. Young.

Opaque

Term applied to materials that absorb light without remission and consequently do not allow light through them.

Transparent

Term applied to materials that allow light to pass through them in straight lines.

Polarization

The aligning of vibrations in a transverse wave, usually by filtering out of other directions.

Umbra

The darker part of a shadow where all the light is blocked.

Light Year

The distance light travels through a vacuum during one year.

When you look at a distant galaxy through a telescope, how is it that you're looking backwards in time?

The light we see was given off by stars years ago- in past.

Electromagnetic Spectrum

The range of electromagnetic waves extended from radio waves to gamma rays.

Some things let light pass through in a diffused direction is?

Translucent.

Some materials let light pass through is?

Transparent.

Light travels in what type of wave?

Transverse

Metals are Opaque. T or F?

True.

T or F. Visible light energy comes out of the glass as the SAME frequency color that it entered in the glass.

True.

Which has the greater energy - Ultraviolet or infrared?

Ultraviolet.

Which has the higher frequency? ultraviolet or infrared?

Ultraviolet.

Which has the shorter wavelengths- ultraviolet or infrared?

Ultraviolet.

Shadows have an area where the light is totally blocked and dark called the?

Umbra

Out atmosphere is transparent to what?

Visible light and some infrared.

Are wavelengths of radio and television signals longer or shorter than waves detectable by the human eye?

Wavelengths and radio and TV signals are much longer than the visible light.

Does time delay between the absorption and remission of light affect the average speed of light in a material? Explain.

Yes. The longer the time delay the slower the average speed.

In terms of the electromagnetic spectrum, what is the relationship between. a. frequency and wavelength? b. frequency and energy?

a. inverse - if frequency increases, wavelength decreases. b. direct - if frequency increases, energy increases.

Light is transmitted when the axes of the polarizing filters are _____.

aligned

A light ____ is considered a bundle of rays.

beam.

Speed of Light goes..

fastest to slowest. vacuum-gas-liquids-solids

Sunglasses are polarized vertically to keep out the strong reflected _______ glare.

horizontal

Rank these in order from lowest to highest frequencies: infrared, visible, and ultraviolet light.

infrared, visible, ultraviolet.

When light strikes matter, electrons in the _____ are forced into vibration. The energy is ______ __.

matter passed on.

When waves move in many different directions they are ?

non polarized

When waves move back and fourth in one direction they are ?

polarized

Light passes through materials whose atoms absorb the energy and immediately ______ it as light

re-emit.

The lowest frequency of light that we can see is ____ and the highest is _________.

red. violet.

Light is absorbed when they are at _____ angles to each other.

right

The Big Idea. Light is the only thing you ____! All visible objects either _____ or ______ light.

see emit reflect

Light travels in what

straight line path.

Glass is _____ to all frequencies of light.

transparent

Rank these in order from shortest to longest wavelengths: light waves, x-rays, or radio waves.

x-rays, light waves, radio waves.