Science Class 10

A beam of light is incident through the holes on side A and emerges out of the holes on the other face of the box as shown in the Figure. Which of the following could be inside the box?

• Concave Lens

• Rectangular Glass Slab

• Prism

• Convex Lens

Rays from Sun converge at a point 15 cm in front of a concave mirror. Where should an object be placed so that size of its image is equal to the size of the object?

• 15 cm in front of the mirror

• 30 cm in front of the mirror

• between 15 cm and 30 cm in front of the mirror

• more than 30 cm in front of the mirror

Beams of light are incident through holes A and B and emerge out of the box through holes C and D respectively as shown in Figure. Which of the following could be inside the box?

• Rectangular Glass Slab

• A Convex Lens

• A Concave Lens

• A Prism

True or False-

Bi-convex and Plano concave mirrors are exceptions to refraction of light

• True

• False

In torches, search lights and headlights of vehicles the bulb is placed

• b/w p and f of the reflector

• very near to the focus of the reflector

• b/w f and C of the reflector

• at C

Three beakers labelled as A, B and C each containing 25 mL of water were taken. A small amount of NaOH, anhydrous CuSO4 and NaCl were added to the beakers A, B and C respectively. It was observed that there was an increase in the temperature of the solutions contained in beakers A and B, whereas in case of beaker C, the temperature of the solution falls. Which one of the following statement(s) is(are) correct?

(i) An exothermic process has occurred in beakers A and B.

(ii) An endothermic process has occurred in beakers A and B.

(iii) In beaker C exothermic process has occurred.

(iv) In beaker C endothermic process has occurred.

• only i

• only ii

• i and iv

• ii and iii

Which of the following gases can be used for the storage of fresh samples of an oil for a long time?

• carbon dioxide or oxygen

• nitrogen or oxygen

• carbon dioxide or helium

• Helium or nitrogen

What happens when a solution of an acid is mixed with a solution of a base in a test tube?

(i) The temperature of the solution increases

(ii) The temperature of the solution decreases

(iii) The temperature of the solution remains the same

(iv) Salt formation takes place

• only i

• i and iii

• ii and iii

• i and iv

During the preparation of hydrogen chloride gas on a humid day, the gas is usually passed through the guard tube containing calcium chloride. The role of calcium chloride taken in the guard tube is to

• absorb the evolved gas

• moisten the gas

• absorb moisture from the gas