Science M.C.Q

Aluminium oxide is amphoteric oxide.

In a relaxed state, the focal length of healthy eyes is 2 cm.

The process of separation of light into its component colours while passing through a medium is called dispersion of light.

The SI unit of specific heat is J/kg °C.

Galvanometer is used for electrical measurements.

The free fall of an object is possible only in vacuum.

While going in an increasing order there is a rise in the molecular mass of the consecutive members of the homologous series by 14 u.

In Wilfley table method to separate particles of gangue gravitation method is used.

The image formed by biconcave lens is always virtual and small.

Ice-ball is prepared from shredded ice again. This is the example of regelation.

The right-hand thumb rule is also called Maxwell’s cork- screw rule.

The groups 1 and 2 constitute the s block.

From the following hydrocarbon benzene is the cyclic hydrocarbon.

For a normal human eye the near point is at 25 cm.

Lights of different colours are used as signal for safety transport. From these, the wavelength of red light is 700 nm.

From the options given below the specific heat of iron is maximum.

A coil of an alloy nichrome is used in electric heater cooker as a resistor.

The value of gravitational acceleration (g) is highest at the poles.

The phenomenon in which compounds having different structural formulae have the same molecular formula is called structural isomerism.

A small hole of changing diameter at the centre of Iris is called pupil.

All the above

Explanation:

Water has a peculiarity property according to which it has maximum density at around 4 degrees Celsius. As we go above or below the mark, the density decreases. Also, the density of ice is lower than that of water. A circulation is thus set up until water in the pond reaches it is maximum density of 4 degrees Celsius.

When at atmospheric temperature reaches 0 degrees Celsius ice begins to form in ponds forming a layer on the top with water below it. If water did not have this property, then it would be impossible for aquatic life to exist in water bodies in cold seasons.

After sufficient thickness of ice is formed it prevents further loss of heat from the bottom layers of water. This is why fishes and other aquatic animals and plants can survive in ponds and other water bodies even when the atmospheric temperature reaches or is well below 0 degrees.

These days when current in the circuit suddenly increases MCB switches are used.

In Modern Periodic Table the number of columns and periods are respectively 18 and 7.

The astronomical object closest to us is the moon.

The gravitational force is much weaker than other forces in nature.

The unsaturated hydrocarbons containing a carbon-carbon double bond are called Alkenes.

Iron is less reactive than aluminium.

All distances parallel to the principal axis are measured from the optical centre.

Refractive index has no unit is the unit of refractive index.

When the temperature of water decreases below 4 °C it’s volume increases.

The frequency of AC is 50 Hz.

In Mendeleev’s periodic table eka- silicon was later named as germanium.

In electrolytic reduction of alumina graphite is used as a cathode.

We can see the Sun even when it is little below the horizon because of refraction of light.Explanation:The rays of light from the Sun travel in straight line until they reach the Earth's atmosphere. The rays of light from the Sun enter obliquely in the Earth's atmosphere. The light rays coming from the Sun bend because of refraction, and this bending increases further because of the further increase in the refractive index of the successive layers. This causes the light rays to bend and we see the Sun early. Similarly, at sunset, the apparent position of the Sun is visible to us and not the actual position because of the same bending of light rays effect. Thus, due to refraction we see the Sun rise about two minutes before it is actually there and during sunset, we see it for around two minutes more, even though it has already moved from that position.

The electricity bill specifies the usage in unit.

In the chemical equation the reactants are written on the left-hand side.

At the time of Mendeleev 63 elements were known.