PHYSICS TEST 4

When a nearsighted person looks at a distant object through her glasses, the image produced by the glasses should be?

At her eyes far point

Real image

Can be seen on a screen

Is sound an EM wave? If not, what kind of wave is it?

Sound is not an EM wave. It is a type of mechanical wave.

If you shine a light through an optical fiber, why does it come out the end but not out the sides?

TIR makes the light reflect from the sides.

What is the angle of refraction when a light ray is incident perpendicular to the boundary between two transparent materials?

The angle of incidence is 0, therefore the refraction angle is 0.

What is the focal length?

The distance from the lens to the principal focus

Where must the film be placed if a camera lens is to make a sharp image of an object far away?

The film must be placed at the focal length of the lens. For objects that are far away, rays coming from the object are parallel and they converge at the focal point of the lens when passed through the lens.

P = 1 / ?

f in meters

m =

hi/ho = -di/do

Snell's law is -

n1sinθ1 = n2sinθ2

Can real images be projected on a screen? Can virtual images? Can either be photographed? Discuss carefully.

A real image (converge at the point of location ) can be projected on a screen, but a virtual image (do NOT converge at the point of location) cannot be projected on a screen. Both can be recorded because lenses can adapt to converging and diverging.

1 / infinity =

0

Which of the following types of electromagnetic radiation travels the fastest? Radio waves, Visible light waves, X-rays, Gamma rays.

All travel at the same speed

In the electromagnetic spectrum, what type of EM wave would have a wavelength of 10^3 km? 1km? 1m?1cm? 1mm? 1mm?

10^3 km - sub radio wave 1km - radio wave 1m - TV signals and microwave 1cm - satellite TV signals and micro waves 1mm - infrared waves and microwaves 1um - infrared waves

Near point

25 cm

Far sighted problems use what for object distance?

25cm

What are convex mirrors?

A mirror that is curved outward like the back of a spoon; passenger mirrors.

Convex mirror

A mirror with a surface that curves outward; virtual, upright and smaller

What shape is a diverging lens?

Concave

Curved mirrors can reflect inside (_____) or outside (_____).

Concave; convex.

Parallel rays are brought to a focus by a __________.

Converging lens.

Positive focal point

Converging lense

Far sighted need _____ to _____.

Converging; bring the rays together.

What shape is a converging lens?

Convex

A negative 1/f is

Convex mirrors; diverging

Units for P

D

To shoot a swimming fish with an intense light beam from a laser gun, you should aim -

Directly at the image

A __________ make parallel light diverge.

Diverging lens.

Negative focal point

Diverging lense

How do eyeglasses help a nearsighted person see more clearly?

Diverging lenses bend light entering the eye, so the image focuses farther from the front of the eye.

Near sighted need _____ to _____ the rays.

Diverging; split.

**Image distance from a second lens

Find first di, subtract from distance between lenses, use that number to find second di.

In empty space, which quantity is always larger for X-ray radiation than for a radio wave?

Frequency

You can tell whether people are nearsighted or farsighted by looking at the width of their face through their glasses. If a person's face appears narrower through the glasses, is the person farsighted or nearsighted?

If you look and a person's face appears narrower through the glasses, then that means they are nearsighted. Nearsighted is corrected with a diverging lens, which is why what you see is reduced in size.

Virtual image

In our head

How does light travel?

In straight lines

Near sighted problems use what for object distance?

Infinity

Negative height of image

Inverted

The image produced on the retina of the eye is _____ compared to the object being viewed.

Inverted

A convex image is behind the _____.

Mirror

If the distance from your eye's lens to the retina is shorter than for a normal eye, you will struggle to see objects that are?

Nearby

If the image is on the left side of the lens it will be _____, if it is on the right side of the lens it will be _____.

Negative; positive.

Archimedes is said to have burned the whole Roman fleet in the harbor of Syracuse, Italy, by focusing the rays of the Sun with a huge spherical mirror. Is this reasonable?

No, the ray will focus into a single point not big enough for an entire harbor.

A concave image is behind the _____.

Object

Virtual images can be formed by -

Plane and curved mirrors, and lenses.

Why are bifocals needed mainly by older persons and not generally by younger people?

Presbyopia is the lessening ability of the eye to accommodate as a person ages and the near point moves out. Far point gets smaller and near point gets larger as you get older.

Which of the following travel at the same speed as light?

Radio waves, Microwaves, Rader, Infrared radiation, cell phone signals, gamma rays, X-rays

An object is placed along the principal axis of a spherical mirror. The magnification of the object is Is the image real or virtual, inverted or upright? Is the mirror concave or convex? On which side of the mirror is the image located?

Real, inverted, same side as object, concave.

Defuse reflection

Reflection of light from a rough surface

Law of reflection

The law relating the angle of incidence of a light ray to the angle of reflection (i=r)

How far are we theoretically supposed to see?

To infinity.

Positive height of image

Upright

Diverging lens image is -

Upright and virtual.

Image "behind" a mirror

Virtual

When the reflection of an object is seen in a flat mirror, the image is -

Virtual and upright

In a vacuum, what is the difference between a radio wave and an X-ray?

Wavelength and frequency.

Total internal reflection

When the angle of incidence is greater than the critical angle.

In attempting to discern distant details, people will sometimes squint. Why does this help?

When you squint it reduces the spherical aberration and the spreading of what you are looking at, which helps you see it better.

Can EM waves travel through a perfect vacuum? Can sound waves?

Yes, EM waves can travel through a perfect vaccum because they do not need any medium for their propagation. The energy of EM waves is varied in the oscillating electric and magnetic fields so no medium is needed. Sound waves can NOT travel through a perfect vaccum.