Slide 1

LightLIGHTLight is a kind of energy that travels in waves.Light can also behave like individual packets of energy called photons.Light can pass through some things, but not others.LIGHTLight travels very fast and in straight lines.

Absorption, Reflection, and TransmissionLight coming in incident light

ReflectionReflection: light that bounces off an object.

TransmissionTransmittance light that passes through an object

AbsorptionAbsorption light that enters an object and is not reflected or transmitted

Absorption, Reflection, and TransmissionWhich forms of light cast a shadow?

Can an invisible person cast a shadow?

Reflected LightAn image can bounce back off an object, such as, a mirror, pond or lake, or shiny metal.

What happens to Absorbed Light?

What happens to Absorbed Light?Light is the kinetic energy of moving photons

Reflected light does not enter the white block. Most of its kinetic energy is reflected as wellWhat happens to Absorbed Light?Light energy that is absorbed by the dark block is transferred to the molecules in the block, causing them to move faster. Heat is therefore produced and radiates from the block.

Spectrophotometer

Spectrophotometer

Concentration

Concentration = mass of solute/volume of solventUnits can be g/L or g/mL

The more solute dissolved, the more concentrated the solution.Concentration Curve

Estimate the Concentration of these samplesAbsorbanceEstimated Concentration (g/mL)0.30____________________0.45____________________0.75____________________

Light and Energy

The Sun, ultimate source of most energy on Earth

Surface = 5,600C

Center = 15,000,000C

75% Hydrogen25% Helium

The 17Nuclear Fusion

Nuclear fusion:Occurs at very high temperature and pressureNuclei of 4 hydrogen atoms fuse togetherForm helium atom and photonLight and EnergyOne helium atom weighs slightly less than 4 hydrogen atomsThe Law of Conservation of Matter states that matter can neither be created of destroyedEinstein concluded that this loss of matter was converted to energy in the form of a photonMatter and energy are related to each other according to Einsteins formula: E = mc2(energy = mass x speed of light2)The 19Resistance in an Incandescent Light Bulb Produces PhotonTungsten filament in a light bulb is very thin and about 2 m longElectrons struggle to pass through the long, thin filament = resistanceFilament heats to about 2,200CThis causes the wire to glow and give off light as photons

Law of ReflectionAngle of Incidence: The angle at which light hits an objectAngle of Reflection: The angle at which light is reflected off an objectLaw of Reflection: the angle at which light hits an object is equal to the angle at which light is reflected from the object ( A = B)

Mirrors

When you look into a mirror, you see a virtual image of the real image reflected in the mirror. It appears the same size and distance from the mirror as the real image. It therefore appears that you are looking into the mirror.Angles of Incidence and Reflection

Determine the angles of incidence and reflection.