Light - Reflection and Refraction — Class 10 Science PYQs

At what distance from a convex lens should an object be placed to get an image of the same size as that of the object on a screen ?

A ray of light falls making an angle of incidence $\theta$ on the surface of a glass slab. Draw a labelled ray diagram to show its path. Also mark lateral displacement on it.

(a) State two laws of refraction of light.

OR

(b) Define the term absolute refractive index of a medium. A ray of light enters from vacuum to glass of absolute refractive index $1.5$. Find the speed of light in glass. The speed of light in vacuum is $3\times 10^8\text{ m/s}$.

(a) State two laws of refraction of light.

OR

(b) Define the term absolute refractive index of a medium. A ray of light enters from vacuum to glass of absolute refractive index $1.5$. Find the speed of light in glass. The speed of light in vacuum is $3\times 10^8\text{ m/s}$.

An object is placed at a distance of $10\text{ cm}$ from a convex mirror of focal length $15\text{ cm}$. Find the position of the image formed by the mirror.

(a) An object is placed in front of a concave mirror of focal length $12\text{ cm}$. If distance of the object from the pole of the mirror is $8\text{ cm}$, then use mirror formula to determine the position of the image formed. Draw a labelled ray diagram to justify your answer in this case.

OR

(b) (i) The image of an object formed by a mirror is real, inverted and is of magnification $-1$. If the image is at a distance of $30\text{ cm}$ from the mirror, where is the object placed ? Give reason to justify your answer.
(ii) Where would the image be if the object is moved $15\text{ cm}$ towards the mirror ? Draw ray diagram for the new position of the object to justify your answer.

(a) Upper half of a convex lens is covered with a black paper. Draw a ray diagram to show the formation of image of an object placed at a distance of $2\text{F}$ from such a lens. Mention the position and nature of the image formed. State the observable difference in the image obtained if the lens is uncovered. Give reason to justify your answer.
(b) An object is placed at a distance of $30\text{ cm}$ from the optical centre of a concave lens of focal length $15\text{ cm}$. Use lens formula to determine the distance of the image from the optical centre of the lens.

(a) Upper half of a convex lens is covered with a black paper. Draw a ray diagram to show the formation of image of an object placed at a distance of $2\text{F}$ from such a lens. Mention the position and nature of the image formed. State the observable difference in the image obtained if the lens is uncovered. Give reason to justify your answer.

OR

(b) An object is placed at a distance of $30\text{ cm}$ from the optical centre of a concave lens of focal length $15\text{ cm}$. Use lens formula to determine the distance of the image from the optical centre of the lens.

Q. Nos. 37-39 are source-based/case-based questions with 2 to 3 short sub-parts. Internal choice is provided in one of these sub-parts :

Study the data given below showing the focal length of three concave mirrors A, B and C and the respective distances of objects placed in front of the mirrors :

Case	Mirror	Focal Length (cm)	Object Distance (cm)
1	A	20	45
2	B	15	30
3	C	30	20

(i) In which one of the above cases the mirror will form a diminished image of the object ? Justify your answer.
(ii) List two properties of the image formed in case 2.
(iii) (A) What is the nature and size of the image formed by mirror C ? Draw ray diagram to justify your answer.
OR
(iii) (B) An object is placed at a distance of $18$ cm from the pole of a concave mirror of focal length $12$ cm. Find the position of the image formed in this case.

Study the data given below showing the focal length of three concave mirrors A, B and C and the respective distances of objects placed in front of the mirrors :

Case	Mirror	Focal Length (cm)	Object Distance (cm)
1	A	20	45
2	B	15	30
3	C	30	20

(i) In which one of the above cases the mirror will form a diminished image of the object ? Justify your answer.
(ii) List two properties of the image formed in case 2.
(iii) (A) What is the nature and size of the image formed by mirror C ? Draw ray diagram to justify your answer.

OR

(iii) (B) An object is placed at a distance of $18\text{ cm}$ from the pole of a concave mirror of focal length $12\text{ cm}$. Find the position of the image formed in this case.