What does a converging (convex) lens do to parallel rays of light?

It reflects the rays back toward the source It refracts the rays so they converge to a focal point on the other side of the lens It spreads the rays out so they diverge on the other side It slows the rays to zero — the lens acts as a barrier

What does a diverging (concave) lens always produce, regardless of where the object is?

A real, inverted, magnified image on the far side of the lens A real, inverted, same-size image at the focal point A virtual, upright, and diminished (smaller) image on the same side as the object No image — diverging lenses only scatter light

What is focal length, and what does a shorter focal length mean?

Focal length is the thickness of the lens at its centre; longer focal length means thicker glass Focal length is the distance from the lens to where parallel rays converge; a shorter focal length means a more powerful (more curved) lens Focal length is the maximum distance at which an object can be seen clearly through the lens Focal length is the diameter of the lens; larger lenses have longer focal lengths

A person with myopia (short-sightedness) cannot focus on distant objects clearly. Which lens corrects this, and why?

A converging (convex) lens — it brings distant rays together before they reach the eye A diverging (concave) lens — it spreads incoming rays so the eye's lens focuses them correctly on the retina A flat lens — it has no effect on the light but reduces glare A very thick converging lens — it slows light enough for the eye to focus

A person with hyperopia (long-sightedness/far-sightedness) cannot focus on nearby objects. Which lens corrects this?

A diverging (concave) lens A converging (convex) lens — it converges incoming rays so the eye can focus nearby objects on the retina A mirror placed in front of the eye No lens is needed — hyperopia corrects itself over time

A camera uses a converging lens to project a real image onto film or a sensor. Where is the sensor placed relative to the focal length?

At exactly the focal point — this is where the image always forms In front of the lens, on the same side as the object Just beyond the focal point — at the image distance for objects at the shooting distance, which is slightly more than the focal length for distant objects At twice the focal length from the lens, always

A microscope uses two converging lenses — the objective and the eyepiece. What does each lens do?

Both lenses do the same job — using two identical lenses doubles the magnification The objective produces a real, magnified image of the specimen; the eyepiece acts as a magnifying glass to further magnify that image The objective collects light; the eyepiece focuses it without magnifying The objective reduces the image to fit on the eyepiece; the eyepiece then expands it

The power of a lens is measured in dioptres. A lens with a focal length of 0.25 m (25 cm) has a power of:

+0.25 dioptres +4 dioptres +25 dioptres −4 dioptres

What is a real image, and what is a virtual image — and which type can be seen on a projection screen?

Both real and virtual images can be projected on a screen A real image is formed where light rays actually converge — it can be projected on a screen. A virtual image is formed where diverging rays appear to come from — it cannot be projected. Virtual images can be projected on a screen; real images can only be seen through a lens Only real images can be seen by the eye; virtual images are invisible

Which lens would you use as a simple magnifying glass, and where do you hold the object for best magnification?

A diverging (concave) lens — hold the object beyond the focal point A converging (convex) lens — hold the object closer to the lens than its focal length, producing a virtual, upright, magnified image A converging lens — hold the object beyond twice the focal length A plane mirror — the flat surface magnifies without distortion