Previous year question of class 10 physics : PYQ's of physics class 10 chapter 1
Q1). What is the real image?
Answer:- if light rays coming from a point, made after reflection, then the image formed is called a real image.
Q2). A stamp collector uses a lens convex of a focal length of 7 cm to examine a stamp. what is the power of the lens?
Answer:- Power=1/f
F=7cm
Power = 1/7
Power=0.1428m.
Q3). Define 1 dioptre of power of a lens.
Answer:- Power of a lens is reciprocal of the focal length. 1 diopter is the power of the lens of focal length 1meter.
Q4). How can you distinguish between plane mirrors, convex mirrors and concave mirrors by merely looking at the image formed in each case?
Answer:- my looking into the mirror and going close to it, in the mirror can be identified.
→ if the image is of the same size and erect then it is a plane mirror.
→ if the image is bigger and erect then it is a concave mirror.
→ if the image is smaller in size and erect then it is a convex mirror.
Q5). Define the principal focus of or.
Answer:- principal focus of a concave mirror is a point on its principal Axis to which all the light rays, which are parallel and close to the axis converge after reflection from the concave mirror.
Q6). State the law of refraction of light?
Answer:-
→ The incident ray, the refracted ray and the normal at the point of incidence all lie in the same plane.
→ the ratio of sin angle of incidence to the sine of refraction is a constant for the given pair of the um.
Sin I/sin r = constant
Q7). If the speed of light in a vacuum is 3×10^8m/s, find the absolute Refractive Index of a medium in which light travel with the speed of 1.4×10^8m/s.
Answer:- speed of light in vacuum, C =3×10^8 m/s
Speed of light in medium, V = 1.4×10^8m/s
Absolute refractive index = speed of light in vacuum/ speed of light in the medium
3×10^8/1.4×10^8 = 2.14
Absolute refractive index = 2sizesizessizesof an object formed by a mirror having a focal length of 20cm, is observed to be reduced to one-third of its size. At what distance the object has been placed from the mirror what is the nature of the image and the mirror?
Q9). Why is the magnification produced by a concave lens is always less than 1?
Answer:- Since the image formed by a concave lens is always smaller than the object. so the magnification produced by a concave lens is always less than.
Q10). Draw a ray diagram showing the path of rays of light when it enters
with oblique incidence (i) from air into the water; (ii) from water into the air.
Answer:-When ray of light enters from air into water, it bends towards the normal as shown:
When a ray of light enters from water into the air, it bends away from the normal as shown :
