Science [2 Mark Questions]

When light strikes with atoms or molecules or particles having size of the order of wavelength of light, first it gets absorbed and then these particles immediately reemits light in different directions with different amounts. Such phenomenon is called "Scattering of light".

As compared to stars, planets are much closer to us. That is why they appear bigger.
Light coming from planet is like a beam of light, coming from cluster of point like sources of light (a collection of large no. of point sized sources of light). Here resultant variation in the amount of light entering our eyes from all the individual and independent pointlike sources comes out to be zero on average, Hence twinkling effects of individual sources are getting nullified. That is why planets do not twinkle.

Damage or malfunction of any part of our visual system causes visual impairment (i.e. loss of sight partly or completely, unclear vision, defect of vision)

Crystalline lens of some people becomes milky and cloudy at old age. Such condition of eye is called "cataract."
→ Person having cataract, may lose vision partially or completely.
→ Nowadays it is quite possible to replace such lens by an artificial lens through "cataract surgery" to restore the vision.

• The change in the direction of light, at the boundary separating the two media, when it passes from one transparent medium to another obliquely, is called refraction of light.

OR

• Bending of light, at the boundary separating the two media, when it travels from one transparent medium to another obliquely, is called refraction of light.

OR

• When a ray of light travels obliquely from one transparent medium to another, its speed changes.
• Therefore at the boundary separating the two media, there occurs a change in its direction of propagation.
• This phenomenon is called refraction of light.

• The change in the direction of light, at the boundary separating the two media, when it passes from one transparent medium to another obliquely, is called refraction of light.

OR

• Bending of light, at the boundary separating the two media, when it travels from one transparent medium to another obliquely, is called refraction of light.

OR

• When a ray of light travels obliquely from one transparent medium to another, its speed changes.
• Therefore at the boundary separating the two media, there occurs a change in its direction of propagation.
• This phenomenon is called refraction of light.

• The rays of light from a swimming fish emerge from river - water and enter into air.
• Thus, they travel from a denser medium to a rarer medium. Therefore they bend away from the normal at the interface.
• Hence, the correct / true position of the fish cannot be determined by the observer from air That is why it is difficult to pierce a fish swimming in a river.

• The field view of a convex mirror is very large, i.e., it gives over-all view of vast area of the backside of a vehicle and it forms a virtual, erect and diminished image of a backside object.
• Hence, the vehicle can be driven safely by viewing backside fully.

• In a headlight, torch and search-light, the light source is placed at the principal focus of a concave mirror.
• As a result, an intense parallel beam of light comes out from a headlight, torch, search-light.

• Concave mirror
• A concave mirror produces an erect and enlarged image of an object, when an object is placed between the pole and principal focus of the concave mirror.

• The image of an object, formed by spherical mirror, can be located by constructing a ray diagram.
• For this, we may arbitrarily consider a large number of rays emanating from a point on an object but for the sake of clarity of ray diagram, it is more convenient to consider only two rays, as the intersection of at least two reflected rays gives the position of the image of the point on that object.

• If a concave mirror is held such that the face is between the pole and principal focus of the concave mirror, a virtual, erect and magnified image of the face is obtained behind the mirror.
• This is of great help in shaving as well as make-up.

• Light is an electromagnetic radiation, which produces the sensation of sight in our eyes.
• Normally, light has a wave nature.

• In comparing two media, the one with the higher refractive index is said to be optically denser than the other.
• The other medium of lower refractive index is said to be optically rarer than the first one.
• The speed of light is higher in an optically rarer medium than in an optically denser medium.
• A ray of light travelling obliquely from an optically rarer medium to an optically denser medium slows down and bends towards the normal at the point of incidence.
• While, when it travels from an optically denser medium to an optically rarer medium, it speeds up and bends away from the normal at the point of incidence.

• The ability of a medium to refract light is expressed in terms of its optical density.
• Optical density has a definite connotation.
• It is not the same as mass density.

• This is because a convex mirror (always) forms an erect, virtual and diminished image of an object, wherever the object may be located.
• Also, a convex mirror has a wider field of view, relative to a plane mirror, as it is curved outwards.
• Thus, a convex mirror fitted on the side of a vehicle enables the driver to view much larger area than that would be possible with a plane mirror, enabling the driver to see traffic behind him/ her to facilitate safe driving.

• Yes.
• The angle of refraction depends on the refractive index of the medium.
• So, bending will vary in different liquids.
• It will be less for a liquid with low refractive index and more for a liquid with high refractive index.
• The refractive index of kerosene as well as that of turpentine oil is more than that of water.
• Hence, the bending will be more for both the oils than in case of water.