A combination of two thin lenses in contact behave as converging lens of focal length 80 cm if one of the lense is convrging lens of focal length 20 cm, the power of other lens will be
Explanation.
f= focul length of combination of two lenses
f1= focul length of ist lens
f2= focul length of 2nd lens
As 1/f =1/f1 + 1/f2
1/80 = 1/20 + 1/f2
1/f2 = 1/80 - 1/20
f2 = -26.66cm
= -0.266 m
As Power of lens P= 1/f (where f will be in meters)
So
P=1/-0.266
= -3.75D
Showing posts with label Formulas. Show all posts
Showing posts with label Formulas. Show all posts
Friday 29 August 2014
Tuesday 6 May 2014
A way to Memorizing Maths and Physics Formulas
Memorizing Math and Physics Formulas
1)..Math and Physics problems are not meant to be studied under stress. Relax your mind. By doing this, you will be able to focus more on your task.
2)..Many people think that once they take a glance at a formula, it is in their mind, but when they wake up the next day, they are shocked to realize that the formula leaked out during the night. This is why it is a good idea to practice solving a problem with the formula without looking it up. You must do this as many times as you can. Repetition leads to Memorization.
3).. Put the raw units of each variable into the formula and see if you can get the units of the answer.
4)..Understand How the Formula is structured. You already have a decent gut feeling about the concept. Make sense of the formula. For instance, a = F / m. F is on the top of the fraction. That makes sense, since if you exert more force on an object, it will speed up more quickly. Mass is on the bottom of the fraction, since more mass means more inertia, making the object more difficult to accelerate. The opposite formula (a = m / F) does not make sense. Using this incorrect formula, a strong force (large number on the bottom of the fraction) would cause a smaller acceleration, which does not make sense.
5).. Find a small book and put down all those formulas. Keep the book at your back pocket and try to review them anytime you feel like you are missing something. This will bring back the memories of what you have learned, making those jaw-breaking formulas stick into your mind forever.
1)..Math and Physics problems are not meant to be studied under stress. Relax your mind. By doing this, you will be able to focus more on your task.
2)..Many people think that once they take a glance at a formula, it is in their mind, but when they wake up the next day, they are shocked to realize that the formula leaked out during the night. This is why it is a good idea to practice solving a problem with the formula without looking it up. You must do this as many times as you can. Repetition leads to Memorization.
3).. Put the raw units of each variable into the formula and see if you can get the units of the answer.
4)..Understand How the Formula is structured. You already have a decent gut feeling about the concept. Make sense of the formula. For instance, a = F / m. F is on the top of the fraction. That makes sense, since if you exert more force on an object, it will speed up more quickly. Mass is on the bottom of the fraction, since more mass means more inertia, making the object more difficult to accelerate. The opposite formula (a = m / F) does not make sense. Using this incorrect formula, a strong force (large number on the bottom of the fraction) would cause a smaller acceleration, which does not make sense.
5).. Find a small book and put down all those formulas. Keep the book at your back pocket and try to review them anytime you feel like you are missing something. This will bring back the memories of what you have learned, making those jaw-breaking formulas stick into your mind forever.
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