A student very cautiously traces the path of a ray through a glass slab for different values of the angle of incidence He then measures the corresponding values of the angle of refraction and the angle of emergence for every value of the angle of incidence. On analysing these measurements of angles, his conclusion would be :
(2)
As angle of incidence is equal to angle of emergence when light ray is passed through the prism, and angle of refraction is smaller than two.
Three students A, B and C focussed a distant building on a screen with the help of a concave mirror. To determine focal length of the concave mirror they measured the distances as given below :
Student A : From mirror to the screen
Student B : From building to the screen
Student C : From building to the mirror
Who measured the focal length correctly ?
Only A
Only B
A and B
B and C
(1)
A concave mirror always forms the image of a distant object at its focus.
If you focus the image of a distant object, whose shape is given below, on a screen using a convex lens.
The shape of the image of this object on the screen would be :
a
b
c
d
(3)
A student is performing the experiment of determining the focal length of a given concave mirror by focussing a distant tree on a screen. Which one of the following kinds of images he is likely to obtain on the screen?
A
B
C
D
(2)
The image formed by concave mirror is real and inverted.
A student has focussed on the screen of distant building using a convex lens. If he has selected a blue coloured building as object, select from the following options the one which gives the correct characteristics of the image formed on the screen.
Virtual, erect, diminished and green shade
Real, inverted, diminished and in violet shade
Real, inverted, diminished and in blue shade
Virtual, inverted, diminished and in blue shade
(3)
As the image is focussed on screen, the image will be real, inverted and diminished but the colour of the image will remain same.
A light ray enters from medium A to medium B as shown in figure. The refractive index of medium B relative to A will be:
greater than unity
less than unity
equal to unity
zero
(1)
As the light ray when travelled from medium A to medium B, then they bend towards the normal which means that medium B has higher refractive index and less speed of light with respect to medium A. So, refractive index of medium B w.r.t. medium A will be greater than unity.
An optical device has been given to a student and he determines its focal length by focusing the image of the sun on a screen placed 24 cm from the device on the same side as the sun. Select the correct statement about the device.
Convex mirror of focal length 12 cm
Convex lens of focal length 24 cm
Concave mirror of focal length 24 cm
Convex lens of focal length 12 cm
(3)
The optical device is a concave mirror because when light rays from a distant object (like Sun) fall on this mirror, its image is formed at the focus of the mirror on same side as the object. Thus, the distance between the mirror and the screen is the focal length of the concave mirror. Hence, focal length of given device is 24 cm.
Select from the following the best experimental set-up for tracing the path of a ray of light through a glass slab :
a
b
c
d
(2)
To achieve best experimental set-up for tracing the path of a ray of light through a glass slab, the point of incidence should be in the middle of the glass slab and the incident angle should be close to 45°.
When you focus the image of a distant flag, whose shape is given below, on a screen using a convex lens, the shape of the image as it appears on the screen is:
(1)
As image is focused on the screen, then the image formed is real. And real images are inverted.
A student determines the focal length of a device ‘X’ by focusing the image of a distant object on a screen placed 20 cm from the device on the same side as the object.
The device ‘X’ is:
Concave lens of focal length 10 cm
Convex lens of focal length 20 cm
Concave mirror of focal length 10 cm
Concave mirror of focal length 20 cm
(4)
In case of the concave mirror, the image will be formed on the same side of the screen at its focus point when object is distant.
