Science 2009 CBSE [ Delhi ] Set II

Sodium, being more reactive than manganese, can be used to reduce manganese from manganese dioxide.

The sky appears blue on a clear day because air scatters short-wavelength light more than longer wavelengths. So, blue light is of short wavelength present at the end of the visible spectrum, and is more strongly scattered in the atmosphere than long wavelength red light.

The speed of light is different in different media. When the ray of light travels from one medium into another it bends because the speed of the light changes.

Water will not be transported from roots to other parts.

Biotic (living organisms) and abiotic( non-living) components.

Tooth enamel is made up of calcium phosphate. When the pH in the mouth decreases the acid becomes strong enough to attack the enamel of the teeth and corrode it. This sets in tooth decay.

Reflex action can be defined as a sudden involuntary action in response to an environmental stimulus.

The compound is Plaster of Paris.

 Plaster of Paris is used in hospitals as plaster for supporting fractured bones in right position.