# help with physics

If we continue heating a piece of initially

room-temperature metal in a dark room,

what will be its first visible color?

1. There will be no color at all.

2. Red

3. Violet

4. White

002 10.0 points

The temperature of your skin is approxi-

mately 37 C.

What is the wavelength at which the peak

occurs in the radiation emitted from your

skin?

003 10.0 points

A quantum of electromagnetic radiation has

an energy of 0.83 keV.

What is its frequency? Planck’s constant is

6.63 × 1034 J · s.

004 10.0 points

An X-ray has a wavelength of 0.0238 nm.

What is the energy of this X-ray? The

speed of light is 2.99792 × 108 m/s and

Planck’s constant is 6.62607 × 1034 J · s.

005 10.0 points

For the following types

visible light

of electromagnetic radiation, how do the

wavelength, frequency, and photon energy

change as one goes from the top of the list

to the bottom?

Wavelength Frequency Photon Energy

1. Increases Decreases Increases

2. Increases Increases Increases

3. Decreases Decreases Increases

4. Increases Decreases Decreases

5. Decreases Increases Increases

006 10.0 points

In the photoelectric effect, the maximum

speed of the electrons emitted by a metal sur-

face when it is illuminated by light depends

on which of the following?

I) Intensity of the light

II) Frequency of the light

III) Nature of the photoelectric surface

1. I only

2. II and III only

3. III only

4. I, II, and III

5. I and II only

007 10.0 points

The light intensity incident on a metallic sur-

face with a work function of 1.1 eV produces

photoeletrons with a maximum kinetic energy

of 2.65 eV.

If the frequency of the light is doubled,

what is the maximum kinetic energy of the

photoeletrons?

008 10.0 points

The photoelectric effect experiment was sig-

nificant because

1. it showed us how to make an instrument

to detect light by converting photons into

brown (cb42578) – Homework 12 – appartaim – (20541) 2

electrons, ultimately leading to the invention

of the television camera.

2. it demonstrated the existence of quan-

tized states in atoms.

3. it proved that atoms cannot exist if the

rules of classical physics were obeyed on the

atomic scale.

4. it led to the development of the Heisen-

berg Uncertainty Principle, a revolutionary

development that forced us to abandon the

idea of determinacy at the atomic scale and

accept that all we can know are the probabil-

ities of future outcomes.

5. it required us to accept the fact that light

can behave like particles, in contrast to the

teachings of classical physics.

009 (part 1 of 2) 10.0 points

The work function for potassium is 2.24 eV.

If potassium metal is illuminated with light

of wavelength 320 nm, find the maximum

kinetic energy of the photoelectrons. The

speed of light is 3 × 108 m/s and Planck’s

constant is 6.62607 × 1034 J · s .

010 (part 2 of 2) 10.0 points

Find the cutoff wavelength.

011 10.0 points

Calculate the de Broglie wavelength for a pro-

ton moving with a speed of 3.2 × 106 m/s.

The mass of a proton is 1.67262 × 1027 kg

and Planck’s constant is 6.62607 × 1034 J · s.

012 10.0 points

At the time of Rutherford’s gold leaf experi-

ment, scientists knew that negatively charged

electrons existed within the atom, but they

did not know where the positive charge

resided.

charge was provided by Rutherford’s exper-

iment?

1. The positive charge must be concentrated

in a small core (the atomic nucleus).

2. The positive charge can freely move

within the atom.

3. There is no positive charge associated

with an atom.

4. The positive charge is spread throughout

the atom.

013 10.0 points

In the Bohr model of the atom, the postulate

stating that the orbital angular momentum of

the electron is quantized can be interpreted in

which of the following ways?

1. The atom is composed of a small, posi-

tively charged nucleus orbited by electrons.

2. An integral number of electron wave-

lengths must fit into the electron’s circular

orbit.

3. An electron has spin of

1

2

.

4. Only one electron can exist in each possi-

ble electron state.

5. An incident photon is completely ab-

sorbed when it causes an electron to move

to a higher energy state.

014 (part 1 of 6) 10.0 points

A hydrogen atom is in the excited state (n =

3).

Using the Bohr theory of the atom, find

the radius of the orbit. The value of ¯h is

1.05 × 1034 J · s .