6.2.4-5 - Uses & Applications of EM Waves & Lenses

Give three practical uses for infrared radiation.

1. Electrical heaters.

2. Cooking food.

3. Infrared cameras.

Give two practical uses for microwave radiation.

1. Satellite communications.

2. Cooking food.

Give two practical uses for radio waves.

1. Television transmission.

2. Radio transmission.

What wave phenomenon is used by lenses to form an image?

refraction

How does a convex lens form an image?

Parallel rays of light are refracted and brought together at a point known as the principal focus.

What is meant by the focal length of a lens?

The distance from the lens to the principal focus.

What is the difference between the image produced by a convex and a concave lens?

• Convex lenses can produce real or virtual images.

• Concave lenses can only produce virtual images.

Why does magnification not have a unit?

• It is the ratio between image height and object height.

• Ratios do not require units.

What symbol is used to represent a convex lens in a ray diagram?

What symbol is used to represent a concave lens in a ray diagram?