Science 8 Unit C Section 2.0Light Behaves in Predictable Ways

2.1 – Light Travels in Rays and Interacts with Materials• The way that we relate to the world

depends on the assumption that light travels to our eyes from objects in straight lines

• Fortunately, light does not twist or turn at will (if it did, it would be like living in a mirror maze or a funhouse with many curved mirrors)

Ray Diagrams

• Light travels in straight lines known as rays

• We can create ray diagrams to show how light travels

• Light will travel in all directions from objects that emit light (such as lightbulbs and stars)

Ray Diagrams and Intensity

• Intensity:

Rays & Shadows

• A shadow is produced when an opaque object blocks light from a light source

Light Interacts With Materials

• Objects can be described as transparent, opaque or translucent

• Transparent:

• Opaque:

• Translucent:

Luminous and Non-Luminous Objects• Luminous:

• Non-Luminous:

Reflections

• As we have previously seen, light will reflect off of objects

• This reflection can be either regular or diffuse

• Regular Reflection:

• Diffuse Reflection:

2.2 – The Law of Reflection

• The Law of Reflection:

2.3 – Reflecting Light With Curved Mirrors• Mirrors can be concave or convex• Although these mirrors follow the

Law of Reflection, their curved surface causes them to focus light onto a point (or away from a point)

Concave Mirror Images

• A concave mirror will focus its rays through the focal point of a mirror

Convex Mirror Images

• Convex mirrors will diverge (spread) light away from its focal point

2.4 – Transparent Substances Refract Light• You may be familiar

with how a straight object appears bent when placed in water

• The object appears bent because the light is bent by the water

What Causes Refraction?

• Refraction is actually caused by a change in the speed of light as it moves from one material to another

• As the light hits a medium of a different density, it will bend away from or towards the normal

• The more dense the new material, the more slowly the light travels, and the more it refracts

Some of the Effects of Refraction

• Refraction causes different colours of light to bend in different amounts

• This is what allows prisms to separate white light into colours

• It also accounts for the rainbow pattern produced when a thin film of oil forms on a water puddle, or the pattern formed on soap bubbles

Lenses Refract and Focus Light

• Lens:

• Lenses can be classified as convex or concave

Concave Lenses

• Concave Lenses cause light to spread or diverge

Convex Lenses

• Convex lenses cause light to converge on a focal point

• These lenses can collect light and will always produce real images