{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

handin08 - Physics 212 Classical and Modern Physics Spring...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
Physics 212 Classical and Modern Physics Spring 2008 Solutions for Hand-In Set #8 A51 — Microscopes (a) No, it couldn’t. The reason is that light has wave- lengths in the 400 nm to 700 nm range, which is much larger than the virus. Sending visible light through a 10-nm slit would create strong diffraction, or bending of the light, and it does the same thing when encountering a 10-nm object. Some of you might be thinking, “But what if I use shorter wavelength light?” Certainly, you can get around the resolution problem by working with 1 nm light, so that diffraction effects aren’t a problem. How- ever, what’s the energy of a 1 nm photon? E ph = 1240 eV · nm 1 nm = 1240 eV This is way more energy than the typical binding energy for chemical bonds in biomolecules (see Problem A 52), so you’ll end up destroying the virus by illuminating it. (b) Let’s find the electron speed that will give a wave- length of 1 nm. By de Broglie we have p = h λ = 6 . 63 × 10 - 34 J · s 10 - 9 m = 6 . 63 × 10 - 25 kg · m/s Now use p = mv to find v = p m = 6 . 63 × 10 - 25 kg · m/s 9 . 11 × 10 - 31 kg = 7 . 28 × 10 5 m/s The energy of these electrons is considerably smaller than the energy of 1 nm photons, and so this is a much less destructive way to image at 1 nm resolution.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}