First of all, what you wrote " أ " is not "alef", it's "hamzah", this is alef " ا ". Now, what you're talking about is called "Tafkheem and Tarqeeq" , "tafkheem" is "thickening" the sound, the letter is pronounced heavy and full, and "tarqeeq" is "softening" the sound, the letter is pronounced lightly. There are 7 heavy/thick letters in Arabic, which are : خ - ص - ض - ط - ظ - غ - ق , the rest of the letters are soft, except for " ر" which have special cases. You can see the difference between light and heavy sounds by comparing "س" (light) and "ص" (heavy) for example. The letter " ا " is pronounced according to the letter before it, so if the letter before it is heavy, it's pronounced heavy as well (even heavier than in "father"), if the letter before it is soft, it becomes soft (as in "apple" or "sad"). For example: سالم "Saalem" = the letter before the " ا " is " س " , a light letter, so the "alef" becomes light ( apple / sad ). صالح "Saaleh" = the letter before " ا " is "ص", a heavy letter, so the "alef" becomes heavy ( heavier than "father" ). I hope it's clear.

The أ pronounces like a in "apple" if it wrote like that " أ " . but it pronounces like a in "father" if it wrote like that " ا " without " ء "

The أ pronounces like a in "apple" if it wrote like that " أ " . but it pronounces like a in "father" if it wrote like that " ا " without " ء "