[电] least mechanical equivalent of light

guāng zuì xiǎo de jī xiè dāng liàng ㄍㄨㄤ ㄗㄨㄟˋ ㄒㄧㄠˇ ㄉㄜ˙ ㄐㄧ ㄒㄧㄝˋ ㄉㄤ ㄌㄧㄤˋ