Science Unit C Flashcards
What did Pythagoras try to explain?
Pythagoras tried to explain how we see light. He thought light consisted of beams. These beams came from a person’s eyes in straight lines, and the sense of sight occurred when these beams touched the objects a person was looking at.
Was this theory true?
There was a problem with this theory. If it were true, then we would be able to see in the dark. In spite of this problem, Pythagoras’s theory was accepted for many years.
What did Euclid try to explain?
Euclid discovered that when you shine a beam of light onto a flat mirror, the angle between the incoming beam and the mirror is equal to the angle between the reflected beam and the mirror. He also suggested that light travels in straight lines.
What did Ptolemy describe?
The astronomer Ptolemy described how light beams bend when they go from air to glass
What did Al-haytham do?
In about A.D. 1000, a great Arab scientist called Al-Haytham took up the study of light. He studied the work of Euclid and Pythagoras and wrote a book on optics
What did Al-haytham show?
He showed that light bounces off objects and then travels to the eye, showing that light does not come from the eyes but rather light travels to the eyes
What happened to Pythagoras´s theory?
Because Al-Haytham’s explanation was so detailed, Pythagoras’s theory was abandoned.
What was Sir Isaac Newton fascinated by?
Sir Isaac Newton also was fascinated by light, and he was especially interested in the colors of a rainbow.
What was Sir Isaac Newton fascinated by?
Sir Isaac Newton also was fascinated by light, and he was especially interested in the colors of a rainbow.
What was Sir Isaac Newton fascinated by?
Sir Isaac Newton also was fascinated by light, and he was especially interested in the colors of a rainbow.
What did Newton show?
By shining a light through a prism, Newton showed that white light is actually a mixture of different colors of light. As the light passed through the prism, it split up into many separate colors. Passing the rainbow colors through a second prism, Newton showed that the separate colors combined back into white light.
When did Ole Romer show his measurment?
The first reasonably accurate measurement was made by Ole Romer in 1676.
Who refined his measurement and when?
His measurement was refined in the 1920s by a scientist named Albert A. Michelson.
What did Ole Romer show?
He placed two mirrors on the tops of two mountains in California and measured the distance between the two mirrors, which was 35.4 km. He then sent a beam of light from one mirror to the other. He used extremely accurate timing devices to measure how long it took the beam to reach the second mountain
What is the earths atmosphere?
The speed of light as it travels through Earth’s atmosphere to be 299 798 km/s.
What are the properties of light?
- Light travels in straight lines.
- Light can be reflected.
- Light can bend.
- Light is a form of energy
Optical device
Is any technology that uses light.
Microscope
Allow you to see great detail by combining the power of at least two lenses
What is a refracting telescope?
Refracting telescopes have two lenses, one on each end of a long tube. The larger lens is the objective lens that gathers light and focuses the rays toward the eyepiece, which in turn allows you to see the object larger than it appears with the unaided eye.
What is a reflecting telescope?
Reflecting telescopes use a large circular mirror that curves inward. This curved surface gathers light extremely well. Another mirror inside the telescope directs light to the eyepiece, which leads to your eye.
What are Binoculars?
They are simply two short refracting telescopes fixed together. Binoculars are not as powerful as telescopes but they are much more convenient.
Ray Diagrams
Scientists use ray diagrams to show how light travels. The light travelling from a source is shown as straight lines called rays. Each ray ends with an arrow to indicate the direction of travel.
How are shadows made?
Ray diagrams also help explain shadows. If light hits an object, it can’t go any farther. So if an object gets between the light and our eyes, we perceive this lack of light as a shadow
Transparent
Transparent materials, such as glass or clear plastic, can transmit light, meaning
light travels straight through them. That’s why you can see clearly through a window pane.
Translucent
Translucent materials allow some, but not all, light to pass through. A frosted window pane is a good example of a translucent material. Some light can pass through, but you can’t see what’s on the other side of the frosted glass in any detail.
Opaque
Opaque materials do not allow any light to pass through them. They absorb or reflect the light that hits them. Since light cannot get through an opaque object, a shadow is created behind it. Wood, metal, and brick are examples of opaque objects.
Non-luminous
Pencils and other opaque objects are non-luminous, meaning they don’t produce light
Luminous
A light source is luminous; it produces light. Light from a light source (the sun, a lamp) bounces or reflects off the pencil and hits your eyes.
Regular reflection
Regular reflection occurs when light rays hit a smooth surface. The incoming rays travel parallel to one another. When these rays strike a smooth surface, they all bounce off in the same direction, and so the reflected rays stay parallel to one another
Diffused reflection
When light rays strike a rough or uneven surface, diffuse reflection occurs. When the light rays hit the surface, they reflect, but due to the rough surface, each of the rays is reflected at a different angle.
Incident Ray
Incident (incoming) rays bounce off as a parallel beam, giving a regular reflection. The shinier and smoother the surface, the better the reflection.
Plane Mirrors
Plane mirrors (flat mirrors) provide the clearest reflections. Using plane mirrors, you can investigate how reflected light behaves.
Normal line
A line perpendicular to the mirror at the point of reflection is called the normal line
Angle of incidence
The angle between the incident ray and the normal is the angle of incidence
Angle of reflection
The angle between the reflected ray and the normal is the angle of reflection.
Law of reflection
According to the law of reflection, the angle of incidence is equal to the angle of reflection.
Concave mirrors
A concave mirror has a surface that curves inward like a bowl. Like any other mirror, concave mirrors obey the law of reflection
Focal point
These rays all head to a common point, called the focal point
Convex mirror
A mirror with a surface curved outward is called a convex mirror. As you might expect, it does the opposite of a concave mirror. Instead of collecting light, it spreads out light rays.
Refraction
refraction is due to changes in the speed of light.
Concave lens
A concave lens is thinner in the centre than at the edges. As parallel rays pass through a concave lens, they have refracted away from the centre of the lens.
Convex lens
A convex lens curves outward and is thicker in the middle than at the edges. As parallel light rays travel through a convex lens, they are refracted toward the centre of the lens. So as light passes through a convex lens, the rays move toward each other.
Real image
Second, a convex lens forms a real image. The light rays actually meet at a point, and the image can be projected onto a screen.
Wave Model of light
Waves and light have two big similarities: they are both a form of energy, and they travel out in all directions. If waves describe light, then you need more information about how waves behave.
Amplitude
The height of a wave from the rest position to the crest (highest point)
Wavelength
The distance from the crest of one wave to the crest of the next
Frequency
The number of times the medium vibrates in a given unit of time
Frequency
The number of times the medium vibrates in a given unit of time
Visible Light Spectrum
When you shine sunlight or white light through a prism, the light refracts, and splits up into the colors of the rainbow. These colors form the visible light spectrum. Each color of light is refracted at a different angle. So white light is made up of many different colors of light.
Radio waves
are vital to communications around the world. Different wavelengths within the
spectrum of radio waves are used to separate modes of communication.
Micro waves
are shorter than radio waves. This means that the frequency of microwaves is higher than radio waves, and they carry more energy. When microwaves are used to heat food, they make the water particles in the food vibrate.
Infrared waves
can’t be seen but they are felt as heat. Special equipment can sense infrared radiation and detect hotter and cooler areas. Images of infrared radiation are called thermograms.
Ultraviolet (UV lights)
UV light carries more energy than visible light and can burn the skin, increasing the risk of skin cancer.
X-Rays
X-rays and gamma rays both represent extremely high-energy radiation. Both these rays can penetrate tissues. Lower energy Rays have difficulty passing through bone, making them useful for medical imaging.
Gamma rays
Gamma rays are used to kill cancer cells
Radar
The word is actually an acronym for radio detection and ranging. Older radar devices used radio waves.
Incandesant light bulb
Incandescent light bulb
At the heart of an incandescent bulb, there is a filament (a thin piece of wire). When you turn it on, electrical energy flows through the filament, heating it to extremely high temperatures. As electricity flows through the filament, it causes the wire to glow white-hot. The light you see from the bulb is the filament glowing.
Fluorescent light bulb
A fluorescent bulb is a glass tube filled with a small amount of gas such as mercury vapor. The inside of the bulb is coated with a white powder called phosphor. Electricity passes through a fluorescent bulb many times per second.
Phosphorescent light bulb
Phosphorescence is slightly different from fluorescence. In fluorescent lights, the phosphor emits light only while the ultraviolet light is hitting it. This ability to emit light is known as phosphorescence. Phosphorescent materials are often used in novelty items because they will glow in the dark for some time after being energized by light
bioluminescence
When living organisms produce their own light, it’s called bioluminescence
photophore
The firefly has a light-producing organ, or photophore, on the underside of its abdomen. The light produced by the photophore is created by a chemical reaction.
Primary colors
red, green, and blue. These three colors are known as the primary colors. If you mix correctly intensities of all three primary colors, you will observe a white light
Secondary colors
This new color is called a secondary color. The secondary colors are cyan, magenta, and yellow
Theory of color addition
This mixing of three colors of light to produce many different colors of light is called the theory of color addition
Pupil
In the human eye, the hole is called a pupil. In a camera, the hole is known as an aperture.
Iris
The pupil is just a hole created by a circular band of muscle called the iris.
Diaphragm
a light sensor directs the diaphragm to change the size of the aperture in the lens to allow in the proper amount of light.
Shutter
The shutter lies behind the aperture. The shutter acts like a set of doors that open when you press the button to take a picture.
Retina
In order to see, light rays must strike the sensitive retina at the back of the eye.
photoreceptors
The retina is a special layer that is filled with photoreceptors, cells that are sensitive to light. There are two types of photoreceptors, rods and cones.
Rods
Rods are highly sensitive to light
Cones
cones detect color
Optic nerve
When light strikes the retina, photoreceptors are stimulated, and they send messages to the optic nerve, which passes the message to the brain.
Film
At the back of the camera is light-sensitive film. When light strikes the film, the film changes chemically, forming an image
Noctural
nocturnal, no animal can see in complete darkness.
Nocturnal
nocturnal, no animal can see in complete darkness.
ommatidium
you will see that each eye is made up of many smaller units. Each individual unit is called an ommatidium.
Pixels
pixels (short for picture elements), much like the individual cards in the stadium picture. Each pixel is assigned coordinates just like the row and seat numbers for a stadium seat.
Resolution
A poorer quality digital image has a low resolution. The resolution of an image refers to the number of pixels per unit area
CCD
A charge-coupled device (CCD)
