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It's well know that Orcs, Golbins, Uruk-hai and most of Sauron's forces don't tolerate light, especially sunlight very well, and certain types of trolls turn to stone when sunlight falls upon them.
One of the best know characteristics of the Uruk-hai are their ability to better withstand sunlight than Orcs or Goblins.
What exactly happens to Orcs when exposed to sunlight?
Do they start to burn like vampires? Do they just lose their strength? Can they not see? Do they just not like it?
This article has a nice analysis of the Orcs aversion to sunlight.
The sunlight seemed to have more of a psychological effect on the orcs, much like the gloom of Mordor depressed the morale of all men who entered there. Many times throughout the Silmarillion Orcs fight in the sunlight, fueled on by either hate of their enemies or fear of their dark masters.
So in a sense they hate the light, and would rather not be in it, but when forced to, they can travel and fight normally. The main passage of interest from LOTR, when Aragorn and company are pursuing the Uruks:
The orc-band began to descend a narrow ravine leading down into the misty plain below. Merry and Pippin, separated by a dozen Orcs or more, climbed down with them. At the bottom they stepped on to grass, and the hearts of the hobbits rose. ‘Now straight on!’ shouted Uglúk. ‘West and a little north. Follow Lugdush.’
‘But what are we going to do at sunrise?’ said some of the Northerners.
‘Go on running,’ said Uglúk. ‘What do you think? Sit on the grass and wait for the Whiteskins to join the picnic?’
‘But we can’t run in the sunlight.’
‘You’ll run with me behind you,’ said Uglúk. ‘Run! Or you’ll never see your beloved holes again. By the White Hand! What’s the use of sending out mountain-maggots on a trip, only half trained. Run, curse you! Run while night lasts!’
Then the whole company began to run with the long loping strides of Orcs. They kept no order, thrusting, jostling, and cursing; yet their speed was very great. Each hobbit had a guard of three. Pippin was far back in the line. He wondered how long he would be able to go on at this pace: he had had no food since the morning. One of his guards had a whip. But at present the orc-liquor was still hot in him. His wits, too, were wide-awake.
According to The Hobbit,
"They don't like the sun; it makes their legs wobble and their heads giddy".
-The Hobbit, Chapter 5: "Riddles in the Dark"
A more thorough explanation is available here.
