There is one place to eat (that is open this week) that is a 3 minute walk from Physics Hall: The Hub. It looks like there are also a few places open in the Memorial Union (e.g. Lance & Ellie's) but the MU is about a 10 minute walk.
There are ~20 restaurants in Campus Town which is within walking distance of Physics Hall. A list and map can be found here.
Many other restaurants are accessible by car or bus. A mostly complete list is available here.
Some restaurants to note:
Hickory Park - popular & somewhat famous, almost exclusively meat dishes
Aunt Maude's - upscale kitsch
The Cafe, Provisions Lot F - upscale, nice atmosphere (owned by same people)
The Spice - upscale Thai
Stomping Grounds - Coffee bar + cafe, nice food and in Campus Town
Taste Place - Good Chinese restaurant for Szechuan dishes
Wok N Roll - Chinese restaurant with reasonable price, good for lunch
Lockwood Cafe - catering to the hippie crowd, excellent food (only open until 3pm)
