Joseph von Fraunhofer discovered that a. passing light through a prism would create a rainbow b. light could behave as a particle c. there were dark lines in the colour spectrum made by the Sun
Absorption lines happen when a. a cool gas absorbs photons b. a hot gas releases photons c. photons pass through empty space
Scientists can study absorption lines to find out a. the masses of stars b. the distances between stars c. the chemicals present in stars
Discussion/essay questions
Do you know any interesting facts about light? What optical illusions or “tricks of the light” have you seen?
Transcript
In 1814, a German physicist named Joseph von Fraunhofer passed light from the Sun through a prism to create a colour spectrum. He noticed that there were dark lines blocking out certain colours in the spectrum. Today, scientists call these lines absorption lines. Absorption lines happen when particles of light, called photons, move through a cool gas. The atoms and molecules in the gas absorb some of the photons and block certain colours of light. When an atom absorbs a photon, it shows up as a dark line in the colour spectrum. The photons that get absorbed are not random. Every element absorbs specific wavelengths of light, which means every element also has a unique pattern of absorption lines. Scientists can study these lines to find out which chemicals are present in stars and planets.
Tetrachromacy causes people to a. be more sensitive to blue light b. see perfectly in the dark c. distinguish more colours than the average person
Tetrachromacy has only been found in a. women b. young children c. artists
Scientists test for tetrachromacy by a. taking a DNA sample b. observing a person’s reactions to bright light c. asking a person to sort nearly identical colours
Discussion/essay questions
Do you think you see colours the same way as other people? Is this possible for us to know?
Transcript
Tetrachromacy is a rare genetic condition that causes some people to see more colours than usual. Most people have three types of cones in their eyes, which are sensitive to red, green, and blue light. However, tetrachromats have four. This allows them to see millions of colours that the average person can’t distinguish. So far, very few true tetrachromats have been identified, and all of them are female. This is because the gene for an extra cone is found on the X chromosome. If men experience the same mutation, they are likely to become colourblind instead. Scientists test for tetrachromacy by asking people to sort nearly identical colours by similarity. The average person will likely change their answer, but a tetrachromat will always sort these colours the same way.
Redshift is one example of how reality can depend on our interpretation. While an observer standing still might be able to see an object change colour, an observer moving at the same speed as the object would not. Can you think of some other situations where different people might interpret reality differently?
Transcript
Redshift is an effect created by light waves. It causes the colour of an object to become redder as it moves away from an observer. This is because red light has the longest wavelength of all the colours on the visible spectrum. Redshift is not something that humans often see, because an object must be travelling very fast to visibly change colour. However, we can observe a similar effect with sound waves, when the pitch of a car horn changes as the car drives away. Redshift is important because it has helped astronomers make observations about the universe. In 1929, the redshift of galaxies caused astronomer Edwin Hubble to discover that the universe is expanding. Today, astronomers also use redshift to find the locations of planets outside of our solar system.
The human perception of colour is caused by the way our eyes to light. While humans can see many different colours, light that is visible to humans only makes up a small amount of the light in the . This is because of the limits of the photoreceptors in our eyes. Human eyes contain types of photoreceptors known as cones, which are responsible for detecting coloured light. Because light is made up of , each type of light has a different wavelength. Cones can pick up on these wavelengths, which is how we differentiate between colours. Humans have three types of cones in our eyes – known as red, green, and blue cones. We can see any colour of light with a wavelength within the range of those cones. However, light outside of the visible range – such as infrared and ultraviolet light – can’t be seen by the human eye. Though this light is invisible to us, it isn’t invisible to every . Different animals have different amounts of cones in their eyes. Dogs, for example, only have two types of cones, and therefore can’t see as many colours as we can. An animal known as the mantis shrimp, however, has sixteen types of cones. That means that its range of visible light is much wider than ours, and it can see colours we can’t even .
Comprehension questions
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Discussion/essay questions
Many scientists have wondered if we all see the same colours, or if we have learned to call different colours the same names. One person could possibly call a colour “red” that another person sees as blue. We have no way of proving or disproving this, because it is difficult to describe what a colour looks like. Do you think it is possible that we all have a different perception of colours?
Transcript
The human perception of colour is caused by the way our eyes respond to light. While humans can see many different colours, light that is visible to humans only makes up a small amount of the light in the universe. This is because of the limits of the photoreceptors in our eyes. Human eyes contain types of photoreceptors known as cones, which are responsible for detecting coloured light. Because light is made up of waves, each type of light has a different wavelength. Cones can pick up on these wavelengths, which is how we differentiate between colours. Humans have three types of cones in our eyes – known as red, green, and blue cones. We can see any colour of light with a wavelength within the range of those cones. However, light outside of the visible range – such as infrared and ultraviolet light – can’t be seen by the human eye. Though this light is invisible to us, it isn’t invisible to every species. Different animals have different amounts of cones in their eyes. Dogs, for example, only have two types of cones, and therefore can’t see as many colours as we can. An animal known as the mantis shrimp, however, has sixteen types of cones. That means that its range of visible light is much wider than ours, and it can see colours we can’t even imagine.
