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View Full Version : Please help ASAP! Optics!


justagirl
May12-04, 02:21 PM
Anyone know how to solve the following problems? Thanks!

1.) An object is placed 12 cm to the left of a diverging lens of focal length
-6cm. A converging lens of focal length 12 cm is placed a distance of d to the right of the diverging lens. Find the distance d that places the final image at infinity.

2.) Light of wavelength 460 nm falls on a diffraction grating with 5000 slits per cm. What is the required ditance from the slits to a screen if the spacing between the first and second dark fringes is to the 0.7m?

Doc Al
May13-04, 08:45 AM
The first problem is a straightforward application of the lens equation:
\frac{1}{f} = \frac{1}{o} + \frac{1}{i}

The second problem requires the equation for diffraction:
d sin\theta = m \lambda

To learn what these equations mean and how to use them, consult your text.