English Medium कक्षा १० - CBSE Important Questions

In flowering plants, the pollen grains are transferred to stigma by pollination but the female germ cells are present in the ovary.
Explain with the help of a labelled diagram (only concerned parts), how the male germ cell reaches the ovary.

Consider the following three flowers namely X, Y and Z. Which flower(s) would develop into a fruit?

Flower X	Flower Y	Flower Z

One half of a convex lens of focal length 10 cm is covered with a black paper. Can such a lens produce an image of a complete object placed at a distance of 30 cm from the lens? Draw a ray diagram to justify your answer. A 4 cm tall object is placed perpendicular to its principal axis of a convex lens of focal length 20 cm. The distance of the object from the lens is 15 cm. Find the nature, position and the size of the image.

A student obtains a sharp image of the distant window (W) of the school laboratory on the screen (S) using the given concave mirror (M) to determine its focal length. Which of the following distances should he measure to get the focal length of the mirror?

A student used a device (X) to obtain/focus the image of a well illuminated distant building on a screen (S) as shown below in the diagram. Select the correct statement about the device (X).

A 4 cm tall object is placed on the principal axis of a convex lens. The distance of the object from the optical centre of the lens is 12 cm and its sharp image is formed at a distance of 24 cm from it on a screen on the other side of the lens. If the object is now moved a little away from the lens, in which way (towards the lens or away from the lens) will he have to move the screen to get a sharp image of the object on it again? How will the magnification of the image be affected?

Explain the following term related to spherical lenses:- optical centre

A student focused the Sun rays using an optical device 'X' on a screen S as shown.

From this it may be concluded that the device 'X' is a (select the correct option)

(A) Convex lens of focal length 10 cm.

(B) Convex lens of radius of curvature 20 cm.

(C) Convex lens of focal length 20 cm.

(D) Concave mirror of focal length 20 cm.

Define the following term in the context of spherical mirrors:- Pole

Define the following term in the context of spherical mirrors:- Centre of curvature

Define the following term in the context of spherical mirrors:- Principal axis

Define the following term in the context of spherical mirrors:- Principal focus

State power of a lens S.I. unit.

Explain the following term related to spherical lenses:- centres of curvature

Explain the following term related to spherical lenses:- principal axis

Explain the following term related to spherical lenses:- principal focus

You have two lenses A and B of focal lengths +10 cm and –10 cm, respectively. State the nature and power of each lens. Which of the two lenses will form a virtual and magnified image of an object placed 8 cm from the lens? Draw a ray diagram to justify your answer

A student obtained a sharp image of a burning candle, placed at the farther end of a laboratory table, on a screen using a concave mirror. For getting better value of focal length of the mirror, the subject teacher suggested him for focusing a well illuminated distant object. What should the student do?

(A) He should move the mirror away from the screen.

(B) He should move the mirror slightly towards the screen.

(C) He should move the mirror as well as the screen towards the newly selected object.

(D) He should move only the screen towards the newly selected object.

Draw a ray diagram to show the formation of the image, when the object is placed between optical centre and principal focus of a convex lens.

State the signs and values of magnifications in the above mentioned case.

A ray of light starting from diamond is incident on the interface separating diamond and water. Draw a labelled ray diagram to show. the refraction of light in this case.