00:01
In the given problem, the matchstick is lighting.
00:07
It means matchstick should be placed at the focal point of the mirror and the rays of heat, say, from a distance heat source like sun, should be incidence parallel to the principal axis of the mirror.
00:27
And we know that when the light rays are, are incidents parallel to the principal axis of the mirror, they pass through the focus and they all converge at the focus.
00:41
So light rays from the sun, those have the heat also inside.
00:48
When they converge at the focus point and then in that case, if a mat stick is placed at the focus point, it will light.
00:59
It will lighten up, right? so, say from the given problem, the case is that the mastic is at the focal point f.
01:10
Now, as per the problem, if we shift both the mirror towards left by one meter distance, like the pole of the mirror was at point p earlier, now it has shifted to point p dash.
01:27
The whole mirror is shifted one meter towards left.
01:32
This distance is 1 meter, right? and the matchstick is also shifted one meter towards the pole.
01:42
Because as per the given problem, suppose the mirror near the mastick and the match stick were both moved and 1 meter towards left.
01:53
So we are moving the mirror towards left, say, from point p to p -dash, and we are also moving met sticks towards left say means from point f which is the focal point of the mirror to the f dash which is the new new location of the mastix so we can say the distance p p -dash is equal to 1 meter and distance f f -dash is also 1 meter so when we shift this way as shown in the figure 2 we have shifted both the mirror and the focus the match stick is still at the focal point of the mirror so it will still light lighten up right so option a is correct option a is means correct yes because the match is still located at the focal point of the mirror that is near to it option a right so this is a say solution for question number 16.
03:12
Now we will move to question number 17.
03:18
So, yeah, is question number 15.
03:21
Yeah, it's question number 15.
03:25
Now here, which of the following statements is obliq are true, right? first statement is say that convex, the focal length of a convex mirror is equal to twice the focal length.
03:43
Length of a concave mirror having the same radius of curvature.
03:48
Now this is statement one is false because the formula focal length is equal to radius of curvature upon 2 is valid for both concave and convex mirrors.
04:07
Right so if one concave and convex mirror have the same radius of curvature they will have the same focal so one is false now part two is say the law of reflection applies at all location on the surface of a convex mirror yes this is true this is true because law of reflection is is valid for the plain surface as well as for the curved surface.
04:50
Laws of reflection, valid for, for means plain and curved surface is both.
05:06
Because as we know, the surface of a same means mirror, spherical mirror, concave mirror is a curved surface.
05:19
So it means loss of reflection also hold at all the points.
05:26
And then we come to option number three.
05:31
It says that reflected parallel beam of light will all pass through the focal point of the mirror.
05:44
Now here, all the beam of the light which are parallel to the principal axis, they will pass through the focal point of the means mirror right reflected right so this third is also right true so in the answer we can say part c second and third are true right we say part c which says second and third are true this is the solution for question number 50 now we go to question number 50 50.
06:49
It says that which one of the following statement is true concerning the radius of curvature of a concave mirror.
06:59
So let us draw the case how we measure the radius of curvature of a concave mirror.
07:07
Let this be a concave mirror like this is the concave mirror and this is the principal axis of concave mirror.
07:22
And the incident rays are coming in same means from right towards left and say example this is a focal point of the concave mirror so those are coming parallel to the principal axes are passing through the focal point and this is the center of curvature this is the pole of the mirror and this distance r is the distance between the in pole and the center of curvature which is nothing but the radius of curvature...