Physics
Grade-7
Easy
Question
____ are widely used in spectacles, microscopes, and telescopes
- Plane mirrors
- Spherical mirrors
- Plane lenses
- Spherical lenses
The correct answer is: Spherical lenses
Related Questions to study
Mathematics
David designs a game for the school fair. Participants roll two number cubes at the same time. If the sum of the numbers on the two cubes is 7, the player wins. About how many winners should Bob expect if 250 participants play this game?
David designs a game for the school fair. Participants roll two number cubes at the same time. If the sum of the numbers on the two cubes is 7, the player wins. About how many winners should Bob expect if 250 participants play this game?
MathematicsGrade-7
Mathematics
When a card is drawn from a well-shuffled pack of 52 cards, what is the probability that it will be an ace?
When a card is drawn from a well-shuffled pack of 52 cards, what is the probability that it will be an ace?
MathematicsGrade-7
Mathematics
19 cards numbered 1, 2, 3………19 are put in a box and mixed thoroughly. One person draws a card from the box. Find the probability that the number on the card is odd.
19 cards numbered 1, 2, 3………19 are put in a box and mixed thoroughly. One person draws a card from the box. Find the probability that the number on the card is odd.
MathematicsGrade-7
Mathematics
There are 40 students in a co-education school, out of which 30 are boys and the rest are girls. From these students, one student is chosen at random; what is the probability that the chosen student is a boy?
There are 40 students in a co-education school, out of which 30 are boys and the rest are girls. From these students, one student is chosen at random; what is the probability that the chosen student is a boy?
MathematicsGrade-7
Mathematics
The number of children in some families is recorded in the table shown below,
|
No. of children |
0 |
1 |
2 |
3 |
4 |
|
No. of families |
5 |
20 |
32 |
10 |
3 |
The number of children in some families is recorded in the table shown below,
|
No. of children |
0 |
1 |
2 |
3 |
4 |
|
No. of families |
5 |
20 |
32 |
10 |
3 |
MathematicsGrade-7
Mathematics
A dental survey of 500 students in a school revealed that 60 of them had two or more cavities. If the total school enrolment is 1500, how many students would you expect to have two or more cavities?
A dental survey of 500 students in a school revealed that 60 of them had two or more cavities. If the total school enrolment is 1500, how many students would you expect to have two or more cavities?
MathematicsGrade-7
Mathematics
Four people conducted an experiment to find how often a flipped coin lands on tails. The results are shown in the table below.
|
Name |
Total flips |
Tails |
|
Brent |
55 |
26 |
|
Bob |
70 |
38 |
|
Amir |
50 |
22 |
|
David |
80 |
41 |
|
Total |
255 |
127 |
Four people conducted an experiment to find how often a flipped coin lands on tails. The results are shown in the table below.
|
Name |
Total flips |
Tails |
|
Brent |
55 |
26 |
|
Bob |
70 |
38 |
|
Amir |
50 |
22 |
|
David |
80 |
41 |
|
Total |
255 |
127 |
MathematicsGrade-7
Mathematics
A 6-sided cube is rolled 10 times and the following numbers come up: 2, 4, 1, 3, 5, 6, 3, 5, 2, 6. Find the experimental probability of getting an odd number.
A 6-sided cube is rolled 10 times and the following numbers come up: 2, 4, 1, 3, 5, 6, 3, 5, 2, 6. Find the experimental probability of getting an odd number.
MathematicsGrade-7
Mathematics
A spinner is found to land on red 
times. If it is spun 200 times, how many times would you expect it to land on red?
A spinner is found to land on red times. If it is spun 200 times, how many times would you expect it to land on red?
MathematicsGrade-7
Mathematics
A coin is flipped 10 times, and the results are H, H, T, H, T, T, T, H, T, T. What is the experimental probability of tails?
A coin is flipped 10 times, and the results are H, H, T, H, T, T, T, H, T, T. What is the experimental probability of tails?
MathematicsGrade-7
Mathematics
A bag contains 14 balls, of which x are black. (i) If one ball is drawn at random, what is the probability that it will be a black ball? (ii) If 4 more black balls are added to the bag, the probability of drawing a black ball is 
. Find the value of x.
A bag contains 14 balls, of which x are black. (i) If one ball is drawn at random, what is the probability that it will be a black ball? (ii) If 4 more black balls are added to the bag, the probability of drawing a black ball is . Find the value of x.
MathematicsGrade-7
Mathematics
The number of children in some families is recorded below in the table shown:
|
No. of families |
15 |
10 |
32 |
20 |
13 |
| No. of Children |
0 |
1 |
2 |
3 |
4 |
The number of children in some families is recorded below in the table shown:
|
No. of families |
15 |
10 |
32 |
20 |
13 |
| No. of Children |
0 |
1 |
2 |
3 |
4 |
MathematicsGrade-7
Mathematics
Deci has designed 12 section spinner game for the exhibition. Participants spin the pointer and win a prize if it lands any of the blue sections. How can Deci determine how many people are likely to be winners if 500 people play their game?
Deci has designed 12 section spinner game for the exhibition. Participants spin the pointer and win a prize if it lands any of the blue sections. How can Deci determine how many people are likely to be winners if 500 people play their game?
MathematicsGrade-7
Mathematics
One card is drawn at random from a well-shuffled pack of 52 cards. What is the probability that the card drawn is either a red card or a king?
One card is drawn at random from a well-shuffled pack of 52 cards. What is the probability that the card drawn is either a red card or a king?
MathematicsGrade-7
Mathematics
The color of cars along a highway was noted over a short period of time and summarised in this frequency table.
|
Color |
White |
Silver |
Blue |
Green |
|
Frequency |
7 |
4 |
5 |
4 |
The color of cars along a highway was noted over a short period of time and summarised in this frequency table.
|
Color |
White |
Silver |
Blue |
Green |
|
Frequency |
7 |
4 |
5 |
4 |
MathematicsGrade-7
