SONAR is used for

• measuring distance, direction, and velocity of objects in the water

• measuring distance, direction, and velocity of objects in the air

• measuring the distance and direction of objects in the water

• measuring direction and velocity of objects in air

How many numbers of particles will be in 8g O₂ molecules?

• 15.1 x 10²³

• 1.51 x 10²³

• 15.1 x 10¹³

• 1.51 x 10¹³

What happens when dry slaked lime reacted with chlorine gas?

• Bleaching powder forms

• Baking soda forms

• Washing soda forms

• Plaster of Paris forms

The melting points (in C) of Sulphur (S), Aluminium (Al), and Iron (Fe) are 113, 666 and 1535, respectively. Which one of the following is correct?

• Only Fe is solid at 200ºC

• Al and Fe are solids at 200ºC

• Fe, Sand Al are solids at 200ºC

• Only S is solid at 200ºC

An electric circuit is set up in such a way that the positive terminal of a battery V is connected to a bulb B₁ which is connected to a resistor R which is connected to bulb B₂. B₂ is finally connected to the negative terminal of the battery. Both the bulbs are glowing. If the value of R is increased, then

• B₂ will become dimmer but the brightness of B₁ will remain unchanged

• Both B₁ and B₂ will remain unchanged

• Both B₁ and B₂ will become dimmer

• B₁ will become dimmer but brightness of B₂ will remain unchanged

Read the given statements and select the correct option.

1. The range of clinical thermometer is from 35ºC to 42ºC
2. The range of laboratory thermometer is usually from 10°C to 110°C.

• Both Statements A and Bare false

• Statement A is correct but Statement B is false

• Statement Bis correct but Statement A is false

• Both Statements A and Bare correct

Which of the following statements are true about image formation in a plane mirror?

1. The image is larger in size than the object.
2. The image is formed at the same distance as the object
3. The image is laterally inverted
4. The image is virtual.

• B, C and D

• A, C and D

• All of these

• A, B and C

A student burns a magnesium ribbon in air and dissolves the ash of the ribbon left after burning in distilled water. On pouring one drop each of this solution, first in blue litmus and then in red litmus solution, he would observe that

• blue litmus turns red, whereas the red litmus remains red

• blue litmus turns red, whereas the red litmus turns blue

• blue litmus turns colorless, whereas the red litmus remains red

• blue litmus remains blue, whereas the red litmus turns blue

"Copper cannot displace zinc from its salt solution. Give the reason."

The following reasons are given by Class VIII students

1. Copper is more reactive than zinc.
2. Copper is less reactive than zinc.
3. Zinc is one of the noble metals.
4. Zinc appears below copper in reactivity series.

Select the correct reason(s) from the reasons given by Class VIII students.

• Only A

• C and D

• Only B

• A and D

80.

Ritu is standing in front of a plane mirror. The distance between Ritu and her image is 10 m. If she moves 2 m towards the mirror, then the distance between Ritu and her image is

• 10 m

• 8 m

• 12 m

• 6 m