Does “軽い勉強” mean “studies that are not important” or “studies that are easy”?

Question

Which of these expresses the meaning "軽い勉強"?

1. "軽い勉強" is really not a natural word pairing. "軽い勉強" just sounds weird?
2. "皆んなは電子辞書によって漢字を調べるので、部首の勉強は軽い勉強になっています。"
   (Because people these days use electronic dictionaries to look-up kanji, studying radicals is not important.)
3. "その新発売のアプリを使えば、部首の勉強は軽くなります。"
   (If you use that new application, the study of radicals becomes much easier to do.)

Answer 1

軽い勉強 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 ちょっとした勉強.

その新発売のアプリを使えば部首の勉強は軽くなる is OK, though it's better to say 手軽｛てがる｝になる instead because 勉強が軽くなる could mean that the study would be shallow or not enough.

皆んなは みんな (or 皆｛みな｝) 電子辞書で によって 漢字を調べるので部首の勉強は軽い勉強になっている can only be interpreted as "studying radicals is not enough because people look them up in electronic dictionaries". (If you really understand what は after みんな mean, ignore my correction.)