LIGHT
What is light?
Light is a form of energy.
Light sources are luminous and give out light. Some examples are the sun, a lamp and flames.
How does light travel?
Energy from light travels in waves. Light waves do not need any particles to travel through, and can travel through vacuums. This is why we can receive light from the sun. It travels at 300,000 km/s (in vacuum)
What are Shadows?
Light travels in straight lines. It cannot travel through opaque objects. This causes a lack of light in the area behind the object. This is the shadow.
How do we see objects?
Non-luminous objects will not give out light. We can only see them because of light bouncing off from luminous objects into our eyes.
What is Transparent?, Translucent?, and Opaque?
There are 3 ways in which objects can let light through. They can:
▪ Be opaque – absorb the light and let nothing through
▪ Be translucent – absorb some of the light and let some through
▪ Be transparent – let the light pass through, or transmit it.
How do mirrors work?
Mirrors work by reflecting. Plane mirrors reflect the exact image, creating a perfect reflection, although it would be inverted. Reflections are caused by light reflecting off mirrors in such a way so that it reflects the things near it in the same direction, and you see the image reflected in the mirror.
The incident ray is the light that travels into a mirror, and the reflected ray is the light reflected off of the mirror. The angle of incidence is the angle at which the light comes into the mirror from the normal, and the angle of reflection is the angle that the light reflects off of the mirror from the normal. The angle of incidence is always equal to the angle of reflection.
What is light?
Light is a form of energy.
Light sources are luminous and give out light. Some examples are the sun, a lamp and flames.
How does light travel?
Energy from light travels in waves. Light waves do not need any particles to travel through, and can travel through vacuums. This is why we can receive light from the sun. It travels at 300,000 km/s (in vacuum)
What are Shadows?
Light travels in straight lines. It cannot travel through opaque objects. This causes a lack of light in the area behind the object. This is the shadow.
How do we see objects?
Non-luminous objects will not give out light. We can only see them because of light bouncing off from luminous objects into our eyes.
What is Transparent?, Translucent?, and Opaque?
There are 3 ways in which objects can let light through. They can:
▪ Be opaque – absorb the light and let nothing through
▪ Be translucent – absorb some of the light and let some through
▪ Be transparent – let the light pass through, or transmit it.
How do mirrors work?
Mirrors work by reflecting. Plane mirrors reflect the exact image, creating a perfect reflection, although it would be inverted. Reflections are caused by light reflecting off mirrors in such a way so that it reflects the things near it in the same direction, and you see the image reflected in the mirror.
The incident ray is the light that travels into a mirror, and the reflected ray is the light reflected off of the mirror. The angle of incidence is the angle at which the light comes into the mirror from the normal, and the angle of reflection is the angle that the light reflects off of the mirror from the normal. The angle of incidence is always equal to the angle of reflection.
And Periscopes?
If you place two mirrors at 45º, you can see over objects since light is redirected with the mirrors. Light from the object first hits the upper mirror and then it is reflected down to the other mirror. It hits the second mirror and then itis reflected in the eye.
What is Refraction?
Light changes direction as it enters denser objects. This causes objects in denser objects like glass or water to appear bent or in a different position to what they actually are. The reason being is because our brain assumes that light doesn’t change direction, and alters the objects appearance because the image isn’t clear to the mind. In refraction, the angle of refraction from the normal is ALWAYS larger than the angle of incidence
And Dispersion?
When white (ordinary) light travels through a glass prism the light changes direction, but also disperses into the colours of the spectrum:
Red Orange Yellow Green Blue Indigo Violet
These are the colours of the spectrum, the seven colours that light is made up of. The prism doesn’t add colour to the light, it just splits the light up. If another glass prism is added upside down later on, the light will recombine into white light again.
The light splits up because all of the colours of the spectrum have different wavelengths, causing refraction to alter the angles in which each one travels, meaning they all move in different directions. Red has the largest wavelength, and the smallest angle of refraction, putting it at the top of the spectrum.
How do we see colours?
Objects absorb and reflect different colours, and this affects what colour we see them in. For example, a red object would only reflect red light, and absorb all other colours of the spectrum. White objects reflect all of the colours of the spectrum and black objects absorb all of them.
If you place two mirrors at 45º, you can see over objects since light is redirected with the mirrors. Light from the object first hits the upper mirror and then it is reflected down to the other mirror. It hits the second mirror and then itis reflected in the eye.
What is Refraction?
Light changes direction as it enters denser objects. This causes objects in denser objects like glass or water to appear bent or in a different position to what they actually are. The reason being is because our brain assumes that light doesn’t change direction, and alters the objects appearance because the image isn’t clear to the mind. In refraction, the angle of refraction from the normal is ALWAYS larger than the angle of incidence
And Dispersion?
When white (ordinary) light travels through a glass prism the light changes direction, but also disperses into the colours of the spectrum:
Red Orange Yellow Green Blue Indigo Violet
These are the colours of the spectrum, the seven colours that light is made up of. The prism doesn’t add colour to the light, it just splits the light up. If another glass prism is added upside down later on, the light will recombine into white light again.
The light splits up because all of the colours of the spectrum have different wavelengths, causing refraction to alter the angles in which each one travels, meaning they all move in different directions. Red has the largest wavelength, and the smallest angle of refraction, putting it at the top of the spectrum.
How do we see colours?
Objects absorb and reflect different colours, and this affects what colour we see them in. For example, a red object would only reflect red light, and absorb all other colours of the spectrum. White objects reflect all of the colours of the spectrum and black objects absorb all of them.