NCERT Solutions
Board Paper Solutions
Ask & Answer
School Talk
Login
GET APP
Login
Create Account
Popular
Latest
Expert Answers
ALL
Raghav Singh
Subject: Science
, asked on 28/2/18
What is arcsine ? How do we calculate it? Will it come(probablity) in the exams?
Answer
2
Nazreen
Subject: Science
, asked on 28/2/18
Q.4. You arc given that the diameter of the eyeball is about 2.3 cm and a normal eye can adjust the focal length of its eye lens to see objects situated anywhere from 25 cm to an infinite distance away from it. What is the power of the (normal) eye lens, when ciliary muscles are fully relaxed?
Answer
1
Raghav Singh
Subject: Science
, asked on 28/2/18
Please tell why u was taken infinity and not v .
Example 1. A person cannot see the object beyond 3 m distinctly. State the nature and focal length of the lens required to correct this defect of vision.
Answer
1
Khushi Jain
Subject: Science
, asked on 28/2/18
Wavelength of blue color is short or size of dust particals,molecules of air?
Answer
1
Rhythm Sehgal
Subject: Science
, asked on 27/2/18
Solve Ques 18,15
Q.15. Draw a ray diagram to illustrate hypermetropia or far sightedness. How is it corrected by using spectacles. Draw a ray diagram to explain it.
Q.18. What is meant by power of lens. Define its SI unit? You have two lens. A and B of focal lengths + 10 cm and - 10 cm respectively. State the nature and power of lens. Which of two lens will form a virtual and magnified image of an object placed 8 cm from the lens. Draw a ray diagram to justify' your answer?
Answer
1
Raghav Singh
Subject: Science
, asked on 27/2/18
Why stars appear slightly higher than their position when viewed from the horizon?
Answer
2
Raghav Singh
Subject: Science
, asked on 27/2/18
In this text there are few questions which remain unanswered. Why electric current flows steadily in the crystals? Why is the speed of electrons slow?how the bulbs light so fast if the flow of electrons is very slow . Please answer these questions . I am very weak at magnet and electricity.
'Flow' of charges inside a wire
How does a metal conduct electricity? You would think that a low-energy electron would have great difficulty passing through a solid conductor. Inside the solid, the atoms are packed together with very little spacing between them. But it turns out that the electrons are able to 'travel' through a perfect solid crystal smoothly and easily. almost as if they were in a vacuum. The 'motion' of electrons in a conductor, however. is very different from that of charges in empty space. When a steady current flows through a conductor. the electrons in it move with a certain average 'drift speed'. One can calculate this drift speed of electrons for a typical copper wire carrying a small current, and it is found to be actually very small, of the order of 1 mm
s
-
1
. How is it then that an electric bulb lights up as soon as we turn the switch on? It cannot be that a current starts only when an electron from one terminal of the electric supply physically reaches the other terminal through the bulb, because the physical drift of electrons in the conducting wires is a very slow process. The exact mechanism of the current flow, which takes place with a speed close to the speed of light, is fascinating, but it is beyond the scope of this book. Do you feel like probing this question at an advanced level ?
Answer
1
M. Arvindh
Subject: Science
, asked on 27/2/18
what are the characteristics of bifocal mirror
Answer
2
Raghav Singh
Subject: Science
, asked on 26/2/18
Please answer this question.
Q.3 In a human eye, which part lubricates the eye by producing mucus and tears?
Answer
2
Payal Arora
Subject: Science
, asked on 26/2/18
Q16 (b) A man with normal near point (25 cm) reads a book with small print using a magnifying glass, a thin convex lens of focal length 5 cm. What is the closest and farthest distance at which he can read the book when viewing through the magnifying glass.
Answer
1
Aakash Kamat
Subject: Science
, asked on 24/2/18
What would be the image distance in a myopic human eye, if an object is kept at i) 25 cm from the eye ii) infinity ?
Answer
1
Pratham
Subject: Science
, asked on 24/2/18
difference between relaxed convex lens and contract convex lens
Answer
1
Nazreen
Subject: Science
, asked on 23/2/18
Explain the fuction of rods and cones in human eye
Answer
6
Diksha Shrivastava
Subject: Science
, asked on 23/2/18
Why sometimes rings are observed around the moon or the sun?
Answer
1
Payal Arora
Subject: Science
, asked on 21/2/18
Why no image is formed on the blind spot ?
Answer
3
Prev
1
2
3
4
5
Next
What are you looking for?
Example 1. A person cannot see the object beyond 3 m distinctly. State the nature and focal length of the lens required to correct this defect of vision.
Q.15. Draw a ray diagram to illustrate hypermetropia or far sightedness. How is it corrected by using spectacles. Draw a ray diagram to explain it.
Q.18. What is meant by power of lens. Define its SI unit? You have two lens. A and B of focal lengths + 10 cm and - 10 cm respectively. State the nature and power of lens. Which of two lens will form a virtual and magnified image of an object placed 8 cm from the lens. Draw a ray diagram to justify' your answer?
How does a metal conduct electricity? You would think that a low-energy electron would have great difficulty passing through a solid conductor. Inside the solid, the atoms are packed together with very little spacing between them. But it turns out that the electrons are able to 'travel' through a perfect solid crystal smoothly and easily. almost as if they were in a vacuum. The 'motion' of electrons in a conductor, however. is very different from that of charges in empty space. When a steady current flows through a conductor. the electrons in it move with a certain average 'drift speed'. One can calculate this drift speed of electrons for a typical copper wire carrying a small current, and it is found to be actually very small, of the order of 1 mm . How is it then that an electric bulb lights up as soon as we turn the switch on? It cannot be that a current starts only when an electron from one terminal of the electric supply physically reaches the other terminal through the bulb, because the physical drift of electrons in the conducting wires is a very slow process. The exact mechanism of the current flow, which takes place with a speed close to the speed of light, is fascinating, but it is beyond the scope of this book. Do you feel like probing this question at an advanced level ?
Q.3 In a human eye, which part lubricates the eye by producing mucus and tears?