List of top Science Questions on Optics asked in CBSE Class X

When you look at an object very close to your eyes, the:
A convex lens of focal length 15 cm, is forming a real image. If the size of image is same as the size of object, then position of object and position of image will be, respectively :

Lenses can form different types of images depending upon their focal length and position of object. A convex lens can create real, inverted or virtual, erect images, while a concave lens forms only virtual and diminished images. The focal length determines the power of lens. Convex lenses have positive focal length while concave lenses have negative focal length by convention. When lenses are placed together, their combined power is determined by the sum of their individual powers.

Identify from the following the ray diagram which shows the correct path of the reflected ray for the ray incident on a concave mirror as shown:

The part of human eye which controls the amount of light entering into it is:

Which one of the sets of observations is not correct and why?
Determine the focal length of the lenses used in the spectacles.
List two causes of this defect.
Name the defect of vision the person is suffering from.
Draw a ray diagram to show image formation for any correct set of observations.
What is the focal length of the convex lens used? Give reason to justify your answer.

Draw a ray diagram to show the formation of a rainbow. Mark on it, points (a), (b) and (c) as given below: 
(a) Where dispersion of light occurs. 
(b) Where light gets reflected internally. 
(c) Where final refraction occurs.

List two conditions necessary to observe a rainbow.
What happens to white light in the above case?
The students in a class took a thick sheet of cardboard and made a small hole in its centre. Sunlight was allowed to fall on this small hole and they obtained a narrow beam of white light. A glass prism was taken and this white light was allowed to fall on one of its faces. The prism was turned slowly until the light that comes out of the opposite face of the prism appeared on the nearby screen. They studied this beautiful band of light and concluded that it is a spectrum of white light
(i) Give any one more instance in which this type of spectrum is observed.
If we want to obtain a real and magnified image of an object by using a concave mirror of focal length 18 cm. Where should the object be placed? Use mirror formula to determine the object distance for an image of magnification -2 by this mirror to justify your answer.
Name the type of lenses required by the persons for the correction of their defect of vision called presbyopia. Write the structure of the lenses commonly used for the correction of this defect giving reason for such designs.
Draw a ray diagram to show the refraction of a ray of light passing through an equilateral glass prism. Mark the angle through which the emergent ray bends from the direction of the incident ray and also name it.
An optical device ‘X’ is placed obliquely in the path of a narrow parallel beam of light. If the emergent beam gets displaced laterally, the device ‘X’ is:
To get an image of magnification -1 on a screen using a lens of focal length 20 cm, the object distance must be: