A luminous object and a screen are placed on an optimal bench and a converging lens is place between them to throw a sharp image of the object on the screen. The linear magnification or
image is found to be 2.5. The lens is now moved 30 cm. nearer the screen and a sharp image again
formed. Calculate the focal length of the lens.

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number of molecules / avogadro's number * molecule molecular = mass

explanation:

we define a gram-molecular weight as the mass of one mole of any element or compound. a mole contains avogadro's number of units (molecules) –  

6.022

x

10

23

. so, dividing the number of molecules by avogadro's number gives us the number of moles. multiplying that by the molecular weight gives us the mass. from the periodic table we find the gram-molecular weight of u to be238 and of f to be19. so,  

u

f

6

will have a gram-molecular weight of 352g.

answer: i dont know the answer but this might

explanation:

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