DIFFERENCES FROM PAST PAPERS (2009)

1. Umbra and Penumbra (see 2002)

2. Heavy water and hard water (see 99)

3. Smog and Smoke (see 2004)

4. Myopia & Hyperopia

Myopia:
Myopia (short sightedness) is an eye disease in which the patient cannot see the distant objects clearly. This disease can be corrected by using convex lenses in glasses.

Hyperopia:
Hyperopia (long sightedness) is defect of vision in which a person cannot see the clearly objects lying close to him. The disease can be corrected by using convex lenses in glasses.

5. Lava and Magma (see 2003)

6. Periscope & Perimeter

Periscope:
Instrument used by submarines to see above the surface of the sea.

Perimeter:
A perimeter is a path that surrounds an area. The word comes from the Greek peri (around) and meter (measure). The term may be used either for the path or its length - it can be thought of as the length of the outline of a shape. The perimeter of a circular area is called circumference.

7. X-rays & Gamma Rays

1. Gamma rays cause more harm to human body than the X- rays.

2. Gamma rays have shorter wavelengths than the X-rays.

3. X rays are emitted by the electrons outside the nucleus, and gamma rays are emitted by the excited nucleus itself.

4. X rays are used in hospitals for taking X-rays but gamma rays are not.