Question

List three optical instruments and describe what they do.

Answer 1

Hint:Instruments that can process light waves to enhance an image to get a better view are referred to as optical instruments. An optical instrument can also be equipped to record an image. So in short, an optical instrument can enlarge or diminish an image and store that image for future use. Some of the optical instruments include the microscope, the camera and the telescope.

Complete answer.
Step 1: List any optical instruments that can enlarge images and record the images.
Optical instruments that enlarge images are the microscope and the telescope.
An optical instrument that records images permanently for future use is the camera.

Step 2: Try to describe the use of these instruments.
To see an object that is very small or more precisely objects like the skin cells, or mineral samples we use a microscope. A microscope consists of two converging lenses and thus a highly magnified image will be obtained. The object to be magnified (eg: plant cell) will be the object for the first lens. The first lens will produce a magnified image of this object. Now the image formed by the first lens will act as the object for the second lens which will form an even more magnified image. This image will be viewed by the observer when looked through the microscope. This microscope is also called a compound microscope.

A telescope is also used to get a magnified image of an object but the object for the telescope will be a very distant one. The telescope may have two or three lenses. The first lens has a large focal length and it will form a real image at its second focal point. The second lens will then magnify this image to form the final inverted image. The telescope is used to observe stars and other cosmic bodies.

A camera is used to record images permanently. When a person clicks the camera, light from the object will fall on the camera which consists of a convex lens. The image formed on the film will be real and inverted. The film is then developed to obtain a photograph. Nowadays the images are recorded digitally.

Note:The converging lens will form a magnified image of the object while the diverging lens will produce a diminished image of the object. The microscope and the telescope are systems with multiple lenses. Each lens will form an image which acts as the object of the next lens and so on. So they can be considered to be working in stages. Terrestrial telescopes have a pair of inverting lenses which will form a final erect image.