Bellwork What is the majority of the volume of an atom?

Bellwork

What is the majority of the volume of an atom?

http://phet.colorado.edu/en/simulation/rutherford-scattering

Light

Isaac Newton theorized that light consisted of tiny particles.

By 1900, evidence supported that light consists of waves.

Is light a particle or a wave?

Wave Properties

Amplitude- wave’s height from zero to crest. Wavelength- length from one point of one wave

to same point on next wave. Frequency- (f) number of wave cycles to pass a

given point per unit of time. Hertz- units of frequency. = cycles/sec Wavelength and frequency are inversely

proportional to one another. Speed of light (c) = wavelength x frequency

Electromagnetic Spectrum

Consists of radiation over several wavelengths. Visible light portion is very small!

Light consists of electromagnetic waves. Electromagnetic Radiation- includes radio

waves, microwaves, infrared waves, visible light, ultraviolet waves, X-rays, and gamma rays.

All waves travel at the speed of light (c), which is 3.0 x 10^8 m/s.

Energy of Light

E = hf

E: Energy in Joules (J) h: Planck’s constant = 6.626 x 10-34 J-s f: Frequency (Hz or s-1)

Wavelength and Frequency

•Wavelength in METERS•Frequency in s-1 (cycles per second)

c = λf

Velocity (speed of light) = wavelength (m) x frequency (s-1)

What is the frequency of yellow light with a

wavelength of 589 nm?

Photoelectric Effect

Einstein used Planck’s theory to explain the Photoelectric Effect: when light hits a metal surface, it can cause electrons to be emitted using certain frequencies of light.

The energy hitting the surface is a “stream of energy packets”: Photons.

Each photon acts like a particle Energy of a photon = hv or E = hv

Calculate the energy of one photon of yellow light with a wavelength of

589 nm.

Atomic Spectra

When an atom absorbs energy, electrons move into higher energy levels.

These electrons lose energy by emitting light when they return to lower energy levels.

Atomic emission spectrum- frequencies of light emitted by an element separate into specific lines.

Each line in an emission spectrum matches to one exact frequency of light emitted by the atom.

No two elements have the same emission spectra. They are like the fingerprints of elements!

Explanation

Electron at ground state By absorbing energy, the energy level rises to

2, 3, 4,or more. Light is emitted and the electron loses energy

as it drops back to ground state.