## Significance of Infinity

Significance of Infinity in Physics and Life
RKDas (MSc- Physics, Banaras Hindu University, India)

Goal:

The author is trying to prove the existence of infinity and infinite energy in the entire universe. By doing so, he raises some basic questions against the profoundly established concepts of prevalent physics.

Introduction to Infinity
In Sanskrit, infinity is termed as ananta, which is something without any limit or end. It is synonymous with Sanskrit term puurna, the full and complete. There is a phonetically similar term apeiron in Greek that stands for potentially unlimited or indefinite.
A specific beauty of the concept of puurna is such that ‘even if a puurna is subtracted or taken out of the puurna, the remainder is but an unreduced puurna itself (puurnasya puurnam aadaaya puurnam eva avashishyate).’ Following the same ideology, a practical statement may be made: the infinity is a one single entity, if there are many infinities, where is the room for placing more than one such infinity? Possibility of multiple infinities defies the basic requirements of infinity, which is not finite or limited.

Review of Zero and Infinity
Zero is a number. The zero, just as a number does exist in reality. It is such a small number or the smallest possible quantity that it is equal to nothing. Zero is an imaginary concept. In reality, ‘zero content’ does not exist; the zero is a no entity; the zero is without a true existence. There is no true zero. Zero is like a pure untruth.
Zero is a greatly useful tool for arithmetic operations. Read more…

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## How was your AISSCE CBSE Class 12 Physics Exam 2013?

How was the CBSE Class 12 Physics Exam today?

Was it easy or difficult?

Many students reported that the questions were unexpected and extra ordinarily tough. What was your experience?

Were there questions beyond your comprehension?

Were there questions out of Syllabus?

Anju R  writes:

Hi,
The Physics CBSE exam was tough.It was not beyond the syllabus but it was confusing and was asked in a twisted manner.Almost all the students who prepared for the exams didnot leave any derivations,laws etc.But the saddest part was that they asked the big derivation for just one mark and only very few were asked.And most questions were unexpected ones.
It was painful when I saw that after the exam almost all the students were crying.Sitting for a whole night for studying the derivations,laws etc.. gave nothing to us other than tears.We were happy after the English exam but the Physics exam gave a terror over us about Board Exams.I think 90 %  of the students could not complete saying that it was a lengthy paper.

During the exam I could see many sitting with great confusion while few others in a hurry to complete  it and the rest of them sitting sadly.By the grace of God I completed 5 minutes before the alloted time and didn’t leave any question.I hope CBSE will consider us.

Yours sincerely,
Anju.R

## Question Bank in Physics Class XII

The collection will also be helpful for students of other syllabuses.

The file consists of syllabus, key points, collection of very short Answer (1 mark), Short answer type question – solved (2 marks), short answers (3 marks), Long answers (5 marks), Solved numericals and 3 sample papers.

The contents are arranged chapter-wise. Any student will find this a boon for easy preparation and to score better marks in Physics.

## Solutions to NCERT Physics Class 12 (Ray Optics)

1. A small candle, 2.5 cm in size is placed at 27 cm in front of a concave mirror of radius of curvature 36 cm. At what distance from the mirror should a screen be placed in order to obtain a sharp image? Describe the nature and size of the image. If the candle is moved closer to the mirror, how would the screen have to be moved?
Answer:Size of the candle, h= 2.5 cmImage size = h’Object distance, u= −27 cmRadius of curvature of the concave mirror, R= −36 cmFocal length of the concave mirror, f=R/2 = -18 cm

Image distance = v

The image distance can be obtained using the mirror formula:

$\frac{1}{u}+\frac{1}{v}=\frac{1}{f}$

$\frac{1}{v}=\frac{1}{f}-\frac{1}{u}$

$=\frac{1}{-18}-\frac{1}{-27}=\frac{-3+2}{54}=-\frac{1}{54}$

Therefore, v=-54cm

Therefore, the screen should be placed 54 cm away from the mirror to obtain a sharp image.

The magnification of the image is given as: $m=\frac{h'}{h}=-\frac{v}{u}$

Therefore, $h'=-\frac{v}{u}\times&space;h&space;=&space;-\frac{-54}{-27}\times&space;2.5&space;=&space;-&space;5&space;cm$

The height of the candle’s image is 5 cm. The negative sign indicates that the image is inverted and real.

If the candle is moved closer to the mirror, then the screen will have to be moved away from the mirror in order to obtain the image.

2. A 4.5 cm needle is placed 12 cm away from a convex mirror of focal length 15 cm. Give the location of the image and the magnification. Describe what happens as the needle is moved farther from the mirror.
3. A tank is filled with water to a height of 12.5 cm. The apparent depth of a needle lying at the bottom of the tank is measured by a microscope to be 9.4 cm. What is the refractive index of water? If water is replaced by a liquid of refractive index 1.63 up to the same height, by what distance would the microscope have to be moved to focus on the needle again?
4. Figures 9.34(a) and (b) show refraction of a ray in air incident at 60° with the normal to a glass-air and water-air interface, respectively. Predict the angle of refraction in glass when the angle of incidence in water is 45º with the normal to a water-glass interface [Fig. 9.34(c)].
5. A small bulb is placed at the bottom of a tank containing water to a depth of 80 cm. What is the area of the surface of water through which light from the bulb can emerge out? Refractive index of water is 1.33. (Consider the bulb to be a point source.)
6. A prism is made of glass of unknown refractive index. A parallel beam of light is incident on a face of the prism. The angle of minimum deviation is measured to be 40°. What is the refractive index of the material of the prism? The refracting angle of the prism is 60°. If the prism is placed in water (refractive index 1.33), predict the new angle of minimum deviation of a parallel beam of light.
7. Double-convex lenses are to be manufactured from a glass of refractive index 1.55, with both faces of the same radius of curvature. What is the radius of curvature required if the focal length is to be 20 cm?
8. A beam of light converges at a point P. Now a lens is placed in the path of the convergent beam 12 cm from P. At what point does the beam converge if the lens is (a) a convex lens of focal length 20 cm, and (b) a concave lens of focal length 16 cm?
9. An object of size 3.0 cm is placed 14 cm in front of a concave lens of focal length 21 cm. Describe the image produced by the lens. What happens if the object is moved further away from the lens?
10. What is the focal length of a convex lens of focal length 30 cm in contact with a concave lens of focal length 20 cm? Is the system a converging or a diverging lens? Ignore thickness of the lenses.
11. A compound microscope consists of an objective lens of focal length 2.0 cm and an eyepiece of focal length 6.25 cm separated by a distance of 15 cm. How far from the objective should an object be placed in order to obtain the final image at (a) the least distance of distinct vision (25 cm), and (b) at infinity? What is the magnifying power of the microscope in each case?
12. A person with a normal near point (25 cm) using a compound microscope with objective of focal length 8.0 mm and an eyepiece of focal length 2.5 cm can bring an object placed at 9.0 mm from the objective in sharp focus. What is the separation between the two lenses? Calculate the magnifying power of the microscope,
13. A small telescope has an objective lens of focal length 144 cm and an eyepiece of focal length 6.0 cm. What is the magnifying power of the telescope? What is the separation between the objective and the eyepiece?
14. (a)A giant refracting telescope at an observatory has an objective lens of focal length 15 m. If an eyepiece of focal length 1.0 cm is used, what is the angular magnification of the telescope?(b) If this telescope is used to view the moon, what is the diameter of the image of the moon formed by the objective lens? The diameter of the moon is 3.48 × 106 m, and the radius of lunar orbit is 3.8 × 108 m.

## SAINIK SCHOOL ENTRANCE EXAM – SAMPLE QUESTION PAPERS, PREVIOUS QUESTION PAPERS

Click on the image above to Download the Previous Question paper for Class 6 Entrance Exam for Sainik Schools

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