CBSE > Class 12 > Physics | CBSE Board | Homework Help

Due to the acceleration 'g' towards vertical direction Hence due to vertor addition of horizontal & vertical acceleration, projectile don't follow a straight line path

0Thank You

ANSWER

Optical and radio telescopes are built on the ground but X- ray astronomy is possible only from a satellite orbiting the earth ,why?

Posted by Suresh Raut 6 years, 4 months ago

CBSE > Class 12 > Physics

0 answers

ANSWER

I want to know all headings of ncert book from ray optics

Posted by Palak Upadhyay 6 years, 4 months ago

CBSE > Class 12 > Physics

1 answers

Prince Raj 6 years, 4 months ago

check ncert book

2Thank You

ANSWER

Will our practicals take place at another centre(school) or internally???

Posted by Aradhya Trivedi 6 years, 4 months ago

CBSE > Class 12 > Physics

1 answers

Řøhăň Řąjpůť ✌️✊ 6 years, 4 months ago

only Delhi region candidate will going to give practicals externally rest have internal practical exams.

6Thank You

ANSWER

How to deal with option type questions

Posted by Sagar Gujjar 6 years, 4 months ago

CBSE > Class 12 > Physics

1 answers

Manasi Jain 6 years, 4 months ago

To deal with MCQs, remember these points- 1. if the (d) option is none of these or all of these, there are 90% chances that its not that one so you have to choose from the other 3. 2. use elimination method. For ex, you know that the answer of the question lies between option (a) or (c) so eliminate (b) and (d) and then solve accordingly and decide the correct one between (a) or (c). 3. might not be in all cases but 80% of times, the answer is option (b) or (c). USE THIS ONLY IF YOU DON'T KNOW THE ANSWER OF THE QUESTION AT ALL! 4. practice. practice. practice. Now, to deal with these, you mainly have to study. This tricks would help but studying and practicing these type of questions is the only way out to score marks. ALL THE BEST!

1Thank You

ANSWER

In 2019-20 which question is coming 99% ?

Posted by Aakash Verma 6 years, 4 months ago

CBSE > Class 12 > Physics

5 answers

Aakash Verma 6 years, 4 months ago

Thnkxx bro

0Thank You

Aakash Verma 6 years, 4 months ago

Thnxx beo

0Thank You

Řøhăň Řąjpůť ✌️✊ 6 years, 4 months ago

This time board is going to set question paper differently so any type of question can be come.. so do questions from SL as well as ncert then do sample paper.

1Thank You

Nishu Godara 6 years, 4 months ago

Ye main topics h ques jrur aayenge inme se

0Thank You

Nishu Godara 6 years, 4 months ago

Moving coil galvanometer/compound microscope/telescope/tramsformer/gauss theorem/meter bridge/potentiometer/galvanometr concerted into volt or ammeter/ TIR/cyclotron/biot savart law/ampere circuit law/lenz law/mutual induction /mirror or lens equation

7Thank You

ANSWER

Define the term wavefront. Using Huygens wave theory, verify the law of reflection

Posted by Aakash Verma 6 years, 4 months ago

CBSE > Class 12 > Physics

1 answers

Gaurav Seth 6 years, 4 months ago

A wavefront is an imaginary surface over which an optical wave has a constant phase. The shape of a wavefront is usually determined by the geometry of the source.

Huygen's principle:

(i) Every point on a given wavefront acts as a fresh source of secondary wavelets which travel in all directions with the speed of light.
(ii) The forward envelope of these secondary wavelets gives the new wavefront at any instant.

Laws of reflection by Huygen's principle:
Let, PQ be reflecting surface and a plane wavefront AB is moving through the medium (air) towards the surface PQ to meet at the point B.

Let, c be the velocity of light and t be the time taken by the wave to reach A' from A.
Then, AA' = ct.

Using Huygen's principle, secondary wavelets starts from B and cover a distance ct in time t and reaches B'.

To obtain new wavefront, draw a circle with point B as centre and ct (AA' = BB') as radius. Draw a tangent A'B' from the point A'.

Then, A'B' represents the reflected wavelets travelling at right angle. Therefore, incident wavefront AB, reflected wavefront A'B' and normal lies in the same plane.

Consider ∆ABA' and B'BA'
AA' = BB' = ct [∵ AA' = BB' = BD = radii of same circle]
BA' = BA' [common]
∠BAA' = ∆BB'A' [each 90°]
∴ ∆ABA' ≅ ∠DBA' [by R.H.S]
∠ABA' = ∠B'A'B [corresponding parts of congruent triangles]

∴ incident angle i = reflected angle r
i.e., ∠i = ∠r

3Thank You

ANSWER

Total marks of chapter EMU

Posted by Sagar Baghel 6 years, 4 months ago

CBSE > Class 12 > Physics

1 answers

Aakash Verma 6 years, 4 months ago

EMI Ya EMU

0Thank You

ANSWER

Why dc cannot pass through a capacitor

Posted by Faraz Shahjahan 6 years, 4 months ago

CBSE > Class 12 > Physics

1 answers

Sia ? 6 years, 4 months ago

A capacitor blocks DC as once it gets charged up to the input voltage with the same polarity then no further transfer of electrons can happen accept to replenish the slow discharge due to leakage if any. hence the flow of electrons which represents electric current is stopped.

1Thank You

ANSWER

Why sunrise is early and sunset is delayed by 2mins

Posted by Sunmeet Kaur Sachdeva 6 years, 4 months ago

CBSE > Class 12 > Physics

2 answers

Vikas Semwal 6 years, 4 months ago

Due to atmospheric refraction

0Thank You

Gaurav Seth 6 years, 4 months ago

During sunrise, when the sun is just below the horizon, our atmosphere causes the light rays to bend and we see the sun early. Similarly, at sunset, the apparent position of the sun is visible to us and not the actual position due to the same bending of light rays effect.

To sum up, due to refraction we see the sun rise about two minutes before it’s actually there and during sunset we see it for around two minutes more, even though it has already moved from that position

3Thank You

ANSWER

Derive. The mirror formula

Posted by Sundar Yadav 6 years, 4 months ago

CBSE > Class 12 > Physics

1 answers

Gaurav Seth 6 years, 4 months ago

The object distance (u), image distance (v) and focal length (f).

The following sign convention is used for measuring various distances in the ray diagrams of spherical mirrors:

All distances are measured from the pole of the mirror.

Distances measured in the direction of the incident ray are positive and the distances measured in the direction opposite to that of the incident rays are negative.

Distances measured above the principal axis are positive and that measured below the principal axis are negative.
?

The figure shows an object AB at a distance u from the pole of a concave mirror. The image A₁B₁ is formed at a distance v from the mirror. The position of the image is obtained by drawing a ray diagram.

Consider the D A₁CB₁ and D ACB

[when two angles of D A₁CB₁ and D ACB are equal then the third angle

But ED = AB

From equations (1) and (2)

If D is very close to P then EF = PF

But PC = R, PB = u, PB₁ = v, PF = f

By sign convention

PC = -R, PB = -u, PF = -f and PB₁ = -v

Equation (3) can be written as

Dividing equation (4) throughout by uvf we get

0Thank You

ANSWER

Capatior

Posted by Ankit Kashyap 6 years, 4 months ago

CBSE > Class 12 > Physics

2 answers

Vivekanand Yadav 6 years, 4 months ago

Those substances which stores energy is called capacitor.

1Thank You

Nitish Mahto 6 years, 4 months ago

Capacitor ek device hai jisme infinte no of charge store kiya ja sakta hai jisme ek +ve terminal or doosra -ve terminal hota hai jiske karan hum infinte no charge store kar sakta hai

0Thank You

ANSWER

To verify the law of combination of resistance by ohm's law

Posted by Abhilasha Kumari 6 years, 4 months ago

CBSE > Class 12 > Physics