Light and Colour
What are the three possible outcomes when light strikes an object?
Reflection, transmission, and absorption
What are the two types of reflection described in the text?
Regular reflection and diffuse reflection.
List the three mediums that light passes through when looking at the fish in the tank.
Water, glass, and air.
What is the name of the transparent front surface of the eye that protects the eye and helps focus light?
Cornea
Name the two main types of telescopes.
Refracting telescope and reflecting telescope.
How are transparent, translucent, and opaque materials different in the way they interact with light?
Transparent: lets most light pass through without scattering, so you can see clearly through it.
Translucent: lets light pass through but scatters it, so details look blurry.
Opaque: does not let light pass through; light is either reflected or absorbed.
Describe a virtual image formed by a plane mirror (mention at least 2 characteristics).
A virtual image in a plane mirror is:
- Upright
- Same size as the object
- Appears behind the mirror
- Has left and right reversed
What happens to the speed of light when it travels from:
a) air -> water
b) water -> glass
c) glass -> air?
a) Air -> water: slows down
b) Water -> glass: slows down even more
c) Glass -> air: speeds up
Which cells in the retina help you see in dim light, and which ones allow you to see colour in bright light?
Dim light: Rods
Colour/bright light: Cones
In a refracting telescope, what are the names of:
a) the large lens that gathers and focuses light, and
b) the lens closest to your eye that magnifies the image?
a) Light-gathering lens: Objective
b) Magnifying lens near eye: Eyepiece
Why does a green leaf appear black in red light, but look green again in green light?
A leaf looks black in red light because there is no green light available for it to reflect. In green light, it looks green again because green wavelengths are present for reflection.
Why do we see a clear image in smooth water but not in choppy water, even though both obey the law of reflection?
Smooth water creates a regular reflection because light rays hit the surface at the same angle, so they reflect uniformly and form a clear image.
Choppy water causes diffuse reflection—each ray hits at a different angle due to the uneven surface, so rays scatter in many directions and the brain cannot form a sharp image.
Why does the ray of light leaving the glass travel in the same direction as it did before entering the water?
The light ray bends while passing through the mediums, but after exiting the glass into air, the net bending cancels out, making the ray continue in a path parallel to the original direction.
Explain how the iris and ciliary muscles work differently when a person looks at something far away versus something close up.
Far away: Iris expands pupil to control light; ciliary muscles relax and lens becomes thin/longer.
Close up: Iris adjusts pupil size; ciliary muscles contract and lens becomes thicker/fatter.
Compare a refracting telescope and a reflecting telescope. What is the key difference in how each instrument gathers and focuses light?
Refracting telescope gathers and focuses light using two convex lenses.
Reflecting telescope gathers and focuses light using a large concave mirror and a small internal mirror to direct the image to the eyepiece.
Why does mixing pigments usually result in darker colours, while mixing light results in brighter colours?
Light mixing adds wavelengths together, producing brighter colours and even white light.
Pigment mixing absorbs more wavelengths and reflects fewer, which makes the result darker. Light gets brighter when mixed, but pigments get darker.
How does the location of the focal point change when a concave mirror becomes more curved? Explain the reason.
The focal point moves closer to the mirror when the concave mirror becomes more curved. This happens because increased curvature makes reflected rays converge (meet) sooner, shortening the distance to the focal point.
Which colour of light bends the most and which bends the least when white light passes through a prism?
Explain how wavelength affects this.
Bends the most: Violet (shortest wavelength)
Bends the least: Red (longest wavelength)
Longer wavelengths bend less; shorter wavelengths bend more. This difference spreads white light into the spectrum.
Why does the brain interpret the image as upright even though the image formed on the retina is upside down?
The brain flips the signals from the optic nerve, interpreting them as upright and combining both eyes into one 3D image.
A doctor uses a laser instead of a scalpel during surgery.
Give two advantages of using laser surgery.
Seals blood vessels as it cuts, which causes less blood loss
Wounds heal faster than scalpel cuts
A student looks at a blue object through a yellow colour filter. Using what you know about complementary colours and pigments, predict what the student will see and explain why.
The student will see the object as black or very dark.
A yellow filter blocks blue light (since yellow and blue are complementary). The blue object needs blue wavelengths to reflect, but the filter prevents blue light from reaching it, so no blue can be reflected into the their eyes.
A security camera is being installed in a store to monitor the largest possible area. Should the store use a plane mirror, concave mirror, or convex mirror in the camera system to assist visibility? State one advantage and one disadvantage.
The store should use a convex mirror.
Advantage: It allows visibility over a larger area than a plane mirror.
Disadvantage: The image is smaller and appears farther away than it really is, but this is acceptable for monitoring since the goal is area, not magnification.
Concave mirrors are not suitable because they either: flip the image (real image, upside down) when the object is far, or magnify but narrow the visible area when the object is close.
Plane mirrors do not show enough area.
A student wants to read small text and see a magnified image on the opposite side of the lens.
Which lens should they use: convex or concave?
Will the image be real or virtual?
Lens to use: Convex lens
Image type: Real image
Reason: A convex lens is thicker in the center and bends light inward to a focal point. When the object is farther than the focal point, the refracted rays meet and form a real image on the opposite side.
A concave lens cannot form real images because the rays never meet.
A student cannot clearly see the board at the front of the classroom, but can read their textbook just fine.
a) What vision problem do they likely have: nearsightedness or farsightedness?
b) Which type of lens would correct it: concave or convex?
c) Explain your answer.
a) Nearsightedness
b) Concave lens
c) The student’s eyeball is likely too long, causing the image to focus in front of the retina. A concave lens spreads out light rays so the image forms correctly on the retina, allowing distant objects (like the board) to become clear.
Why are the images seen through both telescopes and cameras upside down? Hint: think about image formation in optical instruments.
Optical instruments form real images when light rays converge (meet at a point). When the rays cross to form the image, they create an inverted (upside-down) image on film or inside the telescope before it reaches the eye or sensor.