Optics (AQA GCSE Physics): Flashcards
Exam code: 8463
1/410Still learning
Know0
Define lens.
Was this flashcard helpful?
Cards in this collection (41)
Define lens.
A lens is a piece of equipment that forms an image by refracting light.
Define principal focus.
For a convex lens, the principal focus is the point where parallel rays of light are brought to a focus. For a concave lens, it is the point from which parallel rays appear to diverge.
What is another name for a convex lens, and why?
A convex lens is also called a converging lens because parallel rays of light passing through it are brought to a focus.
What is another name for a concave lens, and why?
A concave lens is also called a diverging lens because parallel rays of light passing through it spread out (diverge) from a point.
Define focal length.
The focal length is the distance from the lens to the principal focus.
The more curved a lens is, the ______ its focal length.
The more curved a lens is, the shorter its focal length.
True or False?
A concave lens is sometimes called a converging lens.
False.
A concave lens is sometimes called a diverging lens; it is the convex lens that is called a converging lens.
Define real image.
A real image is formed when light rays from an object converge and meet each other, and can be projected onto a screen.
Define virtual image.
A virtual image is formed when light rays from an object do not meet but appear to meet behind the lens, and cannot be projected onto a screen.
How are real and virtual images represented differently in ray diagrams?
Real images are where two solid lines cross. Virtual images are where two dashed lines, or one dashed and one solid line, cross.
What three properties are used to describe an image formed by a lens?
Whether it is real or virtual, magnified or diminished, and upright or inverted.
What type of image does a convex lens form when the object is placed further from the lens than the focal length f?
A real, magnified, inverted image.
What type of image does a convex lens form when the object is placed closer to the lens than the focal length f?
A virtual, magnified, upright image.
What type of image is always formed by a concave lens?
A virtual, diminished, upright image.
A convex lens produces a real image only when the object is placed at a distance ______ than the focal length from the lens.
A convex lens produces a real image only when the object is placed at a distance greater than the focal length from the lens.
True or False?
The image formed by a convex lens is always real.
False.
A convex lens forms a real image only when the object is further from the lens than the focal length; if the object is closer, the image is virtual.
Define magnification.
Magnification is the ratio of the image height to the object height.
What does the magnification produced by a lens depend on?
The distance of the object from the lens, and the focal length of the lens.
Why does magnification not have units?
Because it is a ratio of two heights measured in the same units.
If the magnification is greater than ______, the image is magnified.
If the magnification is greater than one, the image is magnified.
What does a magnification of exactly one mean?
The object and image are the same size.
True or False?
A magnification of 0.5 means the image is larger than the object.
False.
A magnification less than one means the image is diminished (smaller than the object).
Which colour in the visible spectrum has the longest wavelength?
Red has the longest wavelength, and the lowest frequency and energy.
Which colour in the visible spectrum has the shortest wavelength?
Violet has the shortest wavelength, and the highest frequency and energy.
How are wavelength and frequency related across the visible spectrum?
They are inversely proportional — as wavelength increases, frequency decreases, and vice versa.
An increase in wavelength is a ______ in frequency.
An increase in wavelength is a decrease in frequency.
True or False?
Each colour of the visible spectrum corresponds to a single, exact wavelength.
False.
Each colour corresponds to a narrow band of wavelength and frequency, not a single exact value.
Define specular reflection.
Specular reflection is reflection from a smooth surface in a single direction.
Define diffuse reflection.
Diffuse reflection is reflection from a rough surface that causes scattering.
In specular reflection, how does the angle of reflection r compare to the angle of incidence i?
The angle of reflection r is equal to the angle of incidence i.
Why can a table's surface not produce a clear reflection, even though it may look smooth from afar?
It is actually made up of many tiny ridges, which scatter the light rays that hit it (diffuse reflection).
Diffuse reflection gives objects a ______ appearance, whereas specular reflection gives a shiny appearance.
Diffuse reflection gives objects a dull or matt appearance, whereas specular reflection gives a shiny appearance.
True or False?
In specular reflection, light leaves the surface in all directions.
False.
In specular reflection, light leaves the surface in a single direction; leaving in all directions is what happens in diffuse reflection.
Define white light.
White light is a mixture of all the colours of the visible spectrum.
How does a prism separate white light into a spectrum?
By refraction — violet light is refracted the most and red light is refracted the least.
Define colour filter.
A colour filter works by absorbing certain wavelengths of light and transmitting others.
What happens when white light passes through a red filter?
Red light is transmitted; all other colours are absorbed.
What determines the colour of an opaque object?
The wavelengths of light it reflects most strongly; the wavelengths not reflected are absorbed.
An object appears ______ if all wavelengths of light are absorbed.
An object appears black if all wavelengths of light are absorbed.
What must happen for an object to appear transparent?
All the light must be transmitted, with only a small amount reflected or absorbed.
True or False?
A green surface appears green because it absorbs green light and reflects all other colours.
False.
A green surface reflects green light and absorbs all other colours.
Sign up to unlock flashcards
or