Light

class 8

Give one word for the following :

1. The invisible energy which causes in use the sensation of vision.

2. The ray of light which travels towards a mirror.

3. A line which is drawn at right angles to the mirror surface at the point of incidence.

4. Name one type of mirror which always form virtual image.

5. What type of image is formed on the cinema screen ?

6. Which cells on the retina respond to the intensity of light.

7. The part of the eye which preserves its shape and protects it from external injuries.

8. The phenomenon due to which we can judge depth.

9. The most sensitive part of the retina.

Fill in the blanks :

1. The point at which the incident ray falls on the mirror is called ___________________

2. If a ray of light is incident on a plane mirror at an angle of 300, its angle of reflection is _______________.

3. If a ray of light is incident normally on a mirror, i = __________ and r = ________________

4. The image of our face in a plane mirror is an example of ___________ image.

5. The distance of the image behind the plane mirror is _________ to the distance of the object in front of it.

6. The principle of ___________is made use of in motion picture projection in cinematography.

7. The presence of __________________ cells on the retina helps us to see in dim light.

8. The coned shaped cells of our retina respond to _____________

9. Due to the absence or insufficient number of ____________ cells a person becomes colour blind.

10. Owls and bats are able to see at night due to the presence of ______________ cells in their retina.

LIGHT

class 7

Q.1 Fill in the blanks:-

(i) Light always travels in a ____________.

(ii) Change in direction of light after striking a polished surface is called ____________.

(iii) The phenomenon of left appearing right and right appearing left on reflection from a mirror is called _____________.

(iv) Real images are always ____________ while virtual images are always __________. (erect/inverted)

(v) The reflecting side of a concave mirror curves ____________ while the reflecting side of a convex mirror curves ______________ (inwards/outwards)

(vi) Concave mirrors from ____________ and ____________ images whereas the image formed by a convex mirror is always ____________ (real/virtual)

(vii) ____________ mirrors are used as rear/side view mirrors and ____________ mirrors are used as reflectors of headlights of vehicles.

(viii) A ____________ lens converges rays of light falling on it hence it is also called a ____________ lens.

(ix) A concave lens always forms a ____________ (real/virtual) image which is ____________ (erect/inverted) and ____________ (smaller/bigger) than the object.

(x) Formation of shadows suggest that light travels in __________ lines.

(xi) A __________ lens is thicker in the middle and tapering at the edges.

Water

I.Fill in the blanks:

1.The process by which plants evaporate water is called _________________.

2.The major natural source of water is _________________.

3. Water vapour gets added to the atmosphere by _________________ and ___________________.

4.Water disappears from wet clothes by the process of ___________________.

5. The source of water below the ground such as wells, tubewells, lakes etc. is known as _______.

6. In winter mornings , __________is formed due to condensation of water vapour near the ground.

7. Many tiny water droplets high up in the air, come together and fall down as _____________, __________ and ___________.

8. The amount of the seepage of ________ into the ground affects the availability of ground water.

II. Name the following:

1.Two natural sources of water.

2. Two fresh water bodies.

3.Two rainwater harvesting techniques

4.Four uses of water at home.

5. The two processes through which water vapour enters the air.

6. Two adverse effects of floods.

7. Two adverse effects of drought.

8. Two factors leading to shortage of usable water on the earth.

III. Write true or false:

1. Open wells are fed by ground water:

2. Life is possible on earth without water:

3. Saline water is fit for drinking and other domestic, agricultural and industrial needs:

4. Evaporation of water takes place at all times:

5. Concrete land surfaces increases the seepage of rainwater into the ground:

6. About two-thirds of the earth is covered with water.

7. When water is heated, it changes into ice.

IV. Define the following:

i. Water cycle.

ii. Rainwater harvesting.

V. Distinguish between:a) Evaporation and condensation.

b) floods and droughts