Properties of light
What is the speed of light?
300,000 km/second
What is the cornea and what does it do?
What are the 4 properties of light?
1. Light travels in a straight path
2. Light can be absorbed
3. Light can be reflected
4. Light can be refracted
What is the electromagnetic spectrum?
The electromagnetic spectrum is a continuous range of frequencies for electromagnetic radiation.
Higher frequency = _______ energy
Lower frequency = _______ energy
Higher frequency = more energy
Lower frequency = lower energy
How does light travel?
In waves!
What are the pupil and iris? How do they work together?
The pupil is the black circle in the center of the eye. The iris is the coloured part of the eye surrounding the pupil. The iris is a muscle that contracts or expands the pupil to adjust to the light entering the eye. More light the pupil becomes smaller, less light the pupil becomes bigger.
What is reflection? Give an example of something that reflects light.
Reflection happens when light waves hit the surface of an object and bounce back.
EX) mirrors
What is the visible light spectrum and roughly how many nm does it span?
It is the thin section of the EM spectrum that human vision can perceive (some animals/insects can see more or less). It ranges from 750-400nm.
What colour has the shortest wavelengths? What colour has the longest wavelengths? (In the visible light spectrum)
Blue = shortest
Red = longest
What is wavelength and what does it tell us about light?
It is the distance between peaks of 2 waves and determines the colour we see.
What is the lens? What is it's purpose?
It is the clear and flexible structure located behind the pupil that is held in place by cilliary muslces. It focuses the light into the retina and changes shape (thicken or flatten) to focus on objects at different distances.
What is refraction? Give an example of something that refracts light.
When light passes from one material to another and it changes speed. This causes the light to bend.
EX) Diamonds, glass
What is the longest type of waves of the spectrum and what are they used for?
Radio waves are the longest waves with the lowest energy and lowest frequency. They are used for radio communication.
High amplitude = _____ light
Low amplitude = _____ light
High amplitude = brighter light
Low amplitude = dimmer light
What is amplitude and what does it tell us about light?
It is the height of the wave from rest position to crest of trough and tells us how bright the light is.
What is the retina? What are 2 components of the retina and what do they do?
The retina is a thin layer of tissue at the back of the eye containing photoreceptors (cones & rods). The retina captures light and turns it into electrical signals.Cones allow us to see colour vision and rods allow us to see in low light.
What is absorption? Give an example of something that absorbs light.
Light waves are taken in by a material. The energy from the light is converted into heat.
EX) Dark clothing, metals
What are the shortest waves on the spectrum and what are they used for?
Gamma rays are the shortest waves with the highest energy. They are used to kill cancerous cells (can also cause cancer), sterilize medical equipment and kill bacteria.
What are of the EM spectrum do rays from the sun fall under?
UV rays
What is frequency and what does it tell us about light?
It is how many waves pass by in one second and it linked to the amount of energy in that light.
What is the optic nerve and how does it help us to "see" with our brain?
The optic nerve is a bundle of nerve fibres that connect the eyes to the brain. It transfer the electric signals from the retina to the brain. The brain then interprets these signals as images, thus allowing us to understand what we are seeing.
What is transmission of light? What are the 3types of materials light can transmit through?
When light waves pass through a material.
Transparent: light passes through easily
Translucent: let some light through and scatters it
Opaque: do not allow light to pass through
Draw out the EM spectrum from shortest to longest and label the 7 sections of the spectrum.
radio waves, microwaves, infrared waves, visible light, ultra-violet waves, x-rays, gamma rays
How long does it take for sun's light to reach earth? (distance is about 150 million km)
500 seconds or 8 mins and 20 seconds