When a sound wave goes from one medium to another, the quantity that remains unchanged is:

• Frequency
• Amplitude
• Wavelength
• Speed

If a liquid is heated in space under no gravity, the transfer of heat will take place by process of:

• conduction
• convection
• radiation
• cannot be heated in the absence of gravity

The sun is seen before the actual sunrise because of:

• re?ection
• refraction
• scattering of light
• rectilinear propagation of light

Hydro?uoric acid is not kept in glass bottles because it reacts with:

• visible light
• sodium oxide of glass
• aluminium oxide of glass
• silicon dioxide of glass

Sodium stearate is a salt and is used?

• in gunpowder
• in Paint
• to make Soap
• to make fertilizer

Which of the following copper alloys is used for the manufacture of springs and suspension filaments in electrical instruments?

• Bronze
• Aluminium bronze
• German silver
• Phosphor bronze

What does the airbag, used for safety of car driver, contain?

• Sodium bicarbonate
• Sodium azide
• Sodium nitrite
• Sodium peroxide

Living in the atmosphere of CO is dangerous because it:

• Reduces organic matter of tissues
• Dries up the blood
• Combined with O₂ present inside to form CO₂
• Combines with haemoglobin and makes it incapable of absorbing oxygen

Domestic cooking gas consists of mostly:

• Methane and ethane
• Liquifed butane and isobutane
• Ethylene and carbon monoxide
• Hydrogen and acetylene

Helium is preferred to hydrogen in air balloons because it:

• is cheaper
• is less dense
• has greater lifting power
• does not form an explosive mixture with air