Jag tror att du letar efter samlingen Tales of Ten Worlds (1962).
Den första historien är "Låt det vara lätt" (1957).
En karaktär kritiserade hur dödsstrålarna i science fiction var synliga för det mänskliga ögat och sade att om synligt ljus var dödligt kunde människor inte leva.
The conversation had come around to death rays again, and some carping critic was poking fun at the old science fiction magazines whose covers so often displayed multicoloured beams creating havoc in all directions. ‘Such an elementary scientific blunder,’ he snorted. ‘All the visible radiations are harmless—we wouldn’t be alive if they weren’t. So anybody should have known that the green rays and purple rays and scots-tartan rays were a lot of nonsense. You might even make a rule—if you could see a ray, it couldn’t hurt you.’
Någon såg bilens strålkastare på en svängande bergsvägen på natten och fokuserade ett sökljus genom ett teleskop i bilen, som tillfälligt blundade föraren som körde av en klippa till sin död.
‘At last he saw the headlights of the car flickering on the horizon, and rather reluctantly broke off his observations. When the car had disappeared behind the hill, he was waiting with his hand on the switch. His timing was perfect; the instant the car came round the curve and the headlights shone on him he closed the arc.
‘Meeting another car at night can be unpleasant enough even when you are prepared for it and are driving on a straight road. But if you are rounding a hairpin bend, and know that there is no other car coming, yet suddenly find yourself staring directly into a beam fifty times as powerful as any headlight—well, the results are more than unpleasant.
‘They were exactly what Edgar had calculated. He switched off his beam almost at once, but the car’s own lights showed him all that he wanted to see. He watched them swing out over the valley and then curve down, ever more and more swiftly, until they disappeared below the crest of the hill.
Och den andra berättelsen är "Ett litet fall av solstråle" (1958).
Tusentals människor vinklade spegelliknande föremål i rätt vinklar för att koncentrera solljuset tusentals gånger på sitt offer som dödades av den intensiva värmen.
En missnöjd fotbollsmatchare sköt domaren, per den här översynen :
Some of the home audience became hysterical with anger and threatened to storm the field, but not the disciplined military personal among them. After the teams retreated to the sidelines, leaving the head r eferee isolated in the center of the field, there was a shrill bugle sound, and in unison the military personal each lifted his shinny program and angled it in the bright sunlight. All those programs formed a giant, curved mirror, with the focal point dire ctly on the referee. With a brilliant flash, the referee was transformed into a "smoldering heap" from which rose a column of smoke. In some countries, soccer is taken quite seriously.
Hittade med Google-frågan "arthur c clarke" "visible light" som returnerade Wikipedia-sidan av "Låt det vara lätt" . Jag skummade sedan historierna i de viktigaste samlingarna fram till jag fann "Ett litet fall av solstråle".