Does "軽い勉強" mean "studies that are not important" or "studies that are easy"? Which of these expresses the meaning ""? 1. "" is really **not** a natural word pairing. "" just sounds weird? 2. "" (Because people these days use electronic dictionaries to look-up kanji, studying radicals is _not important_.) 3. "" (If you use that new application, the study of radicals _becomes much easier_ to do.)

is not an unnatural expression and it usually means something that's not necessarily supposed to be a study but virtually functions as a kind of study, or a handy and partial learning exercise, which are synonymous to .

is OK, though it's better to say instead because could mean that the study would be shallow or not enough.

~~~~ (or ) ~~~~ can only be interpreted as "studying radicals is not enough because people look them up in electronic dictionaries". (If you really understand what after mean, ignore my correction.)