List of top Questions asked in CBSE Class X

100 surnames were randomly picked up from a local telephone directory and the frequency distribution of the number of letters in the English alphabets in the surnames was obtained as follows:

Number of letters	1 - 4	4 - 7	7 - 10	10 - 13	13 - 16	16 - 19
Number of surnames	6	30	40	16	4	4

Determine the median number of letters in the surnames. Find the mean number of letters in the surnames? Also, find the modal size of the surnames.

The refractive index of diamond is 2.42. What is the meaning of this statement?

You are given kerosene, turpentine and water. In which of these does the light travel fastest? Use the information given in Table.
$refractive index of some material media$

Find out, from Table, the medium having highest optical density. Also find the medium with lowest optical density.

Light enters from air to glass having refractive index 1.50. What is the speed of light in the glass? The speed of light in vacuum is 3 × 10⁸ m s⁻¹.

The distribution below gives the weights of 30 students of a class. Find the median weight of the students.

Weight (in kg)	40 - 45	45 - 50	50 - 55	65 - 60	70- 65	65 - 70	70 - 75
Number of students	2	3	8	6	6	3	2

A ray of light travelling in air enters obliquely into water. Does the light ray bend towards the normal or away from the normal? Why?

A concave mirror produces three times magnified (enlarged) real image of object placed at 10 cm in front of it. Where is the image located?

Find the focal length of a convex mirror whose radius of curvature is 32 cm.

Why do we prefer a convex mirror as a rear-view mirror in vehicles?

Name the mirror that can give an erect and enlarged image of an object.

The radius of curvature of a spherical mirror is 20 cm. What is its focal length?

Define the principal focus of a concave mirror.

A student noted the number of cars passing through a spot on a road for 100 periods each of 3 minutes and summarised it in the table given below. Find the mode of the data :

Number of cars	0 - 10	10 - 20	20 - 30	30 - 40	40 - 50	50 - 60	60 -70	70 - 80
Frequency	7	14	13	12	20	11	15	8

The given distribution shows the number of runs scored by some top batsmen of the world in one-day international cricket matches.

Runs scored	Number of batsmen
3000 - 4000	4
4000 - 5000	18
5000 - 6000	9
6000 - 7000	7
7000 - 8000	6
8000 - 9000	3
9000 - 10000	1
10000 - 11000	1

Find the mode of the data.

The following distribution gives the state-wise teacher-student ratio in higher secondary schools of India. Find the mode and mean of this data. Interpret the two measures.

Number of students per teacher	Number of states / U.T
15 - 20	3
20 - 25	8
25 -30	9
30 - 35	10
35 - 40	3
40 - 45	0
45 - 50	0
50 - 55	2

The following data gives the distribution of total monthly household expenditure of 200 families of a village. Find the modal monthly expenditure of the families. Also, find the mean monthly expenditure :

Expenditure (in Rs)	Number of families
1000 - 1500	24
1500 - 2000	40
2000 - 2500	33
2500 - 3000	28
3000 - 3500	30
3500 - 4000	22
4000 - 4500	16
4500 - 5000	7

The following data gives the information on the observed lifetimes (in hours) of 225 electrical components :

Lifetimes (in hours)	0 - 20	20 - 40	40 - 60	60 - 80	80 - 100	100 - 120
Frequency	10	35	52	61	28	29

Determine the modal lifetimes of the components.

A copper wire has diameter 0.5 mm and resistivity of $1.6×10^{–8} \ Ω m$. What will be the length of this wire to make its resistance 10 Ω? How much does the resistance change if the diameter is doubled?

The values of current I flowing in a given resistor for the corresponding values of potential difference V across the resistor are given below -

I (amperes)	0.5	1.0	2.0	3.0	4.0
V (volts)	1.6	3.4	6.7	10.2	13.2

Plot a graph between V and I and calculate the resistance of that resistor.

The following table shows the ages of tha year:

Age (in years)	5 - 15	15 - 25	25 - 35	35 - 45	45 - 55	55 - 65
Number of patients	6	11	21	23	14	5

Find the mode and the mean of the data given above. Compare and interpret the two measures of central tendency.

Explain the following.

Why is the tungsten used almost exclusively for filament of electric lamps?
Why are the conductors of electric heating devices, such as bread-toasters and electric irons, made of an alloy rather than a pure metal?
Why is the series arrangement not used for domestic circuits?
How does the resistance of a wire vary with its area of cross-section?
Why are copper and aluminium wires usually employed for electricity transmission?

Why is damage to the ozone layer a cause for concern? What steps are being taken to limit this damage?

If all the waste we generate is biodegradable, will this have no impact on the environment?

What are the problems caused by the non biodegradable wastes that we generate?