CHEM 18 L1 - Nature of Light

Christian Huygens (Dutch physicist) believed that light was made up of what?

Light is made up of waves that are vibrating up and down, perpendicular to the light’s travel direction

Wave

A disturbance that transmits energy

Electromagnetic radiation consists of what two fields?

Oscillating magnetic and electric fields at right angles to each other

Frequency

It is the number of complete waves passing through a point per time

Velocity of wave (λ x v)

It is the distance a wave font travels in a unit of time

In a vacuum, EMR moves at what speed?

Speed of light (C) = wavelength (λ) x frequency (v)

Rank the Electromagnetic spectrum from lowest to highest energy

radio, microwave, infrared, visible, ultraviolet, x-ray, gamma ray

What is the speed of light?

C = 3.0 x 10^8 m/s

The yellow light given off by a sodium vapor lamp used for street lighting has a wavelength of 589 nm. What is the frequency of this radiation?

5.09 x 10^14 s^-1

The green light corresponds to a wavelength of 486 nm. What is the frequency of this light?

6.17 x 10^14 s^-1

Continuous spectrum

An emission spectrum of white light or sunlight

Line spectrum

An emission spectrum of atoms in the gas phase - narrow colored lines, each being light of particular wavelength and definite E

What led Einstein to believe that light was a particle?

Shadows have edges that were sharp and clear

Who studied the EMR emitted by solids heated to various temperatures?

Max Planck (1900) Blackbody Radiation

In blackbody radiation, does the radiation depend on temperature or the element the solid is made of?

Temperature

Radiation consists of packets of energy that is represented by?

E = h x v (frequency), h = 6.626 x 10^-34 Js

In Max Planck’s Quantum Theory, what type of light is made of photons of the same frequency or energy?

Monochromatic light

Intensity of light depends on what quantity?

Number of photons emitted per second

Photoelectric effect

It is the phenomena where electron beams (or electricity) is produced when a beam of light (photons) shines on certain surfaces (e.g., some metals)

Kinetic Energy (KE) depends on (intensity, frequency, wavelength)

Frequency

Which produces higher energy: dim blue light or bright red light

dim blue light

A bundle with lower threshold energy can dislodge an electron from atomic nuclei

False

What happens to the excess energy (when v > vo)

Becomes KE

Quanta

Units of energy

Interference

Wave property where waves superpose and pass through each other

Diffraction

Wave property where waves spill of edges of obstructions

Polarization

Wave property eliminating one of light’s fields

Describe the 3 particle properties (Travel direction, reflection, refraction)

Travels in straight lines, changes direction when hitting certain objects, bends when going through materials)