please explain briefly the difference between angular magnification & linear magnification
Linear magnification is the ratio of the image to the object using either size or distance (linear magnification = image height/object height = distance to image/distance to object). When calculating, assign a negative value to the image. The resulting magnification will then have a negative or positive value indicating a real or virtual image.
Microscopes and telescopes produce a virtual image at infinite distance in the eyepiece. Instead of linear magnification, these instruments rely on angular magnification.
Magnification in Microscopes
The total magnification of a microscope is determined by the ocular lens magnification multiplied by the objective lens magnification (magnification = ocular lens x objective lens).
Magnification in Telescopes
Magnification in telescopes is calculated by dividing the focal length of the objective lens by the focal length of the eyepiece (magnification = telescope focal length/eyepiece focal length).