Phases of the moon occur because: (a ) we can see only that part of the moon which reflects light towards us. (b) our distance from the moon keeps changing. (c) the shadow of the Earth covers only a part of the moon’s surface. (d) the thickness of the moon’s atmosphere is not constant.
Moon revolves around the earth in its own orbit. Sun is the principal source of light, hence, the part of sunlight which gets reflected after falling on the moon is visible to us as phases. So we can see only that part of the moon which reflects light towards us.
