Монохроматический точечный источник света в оптической системе, представленной на рисунке, излучает свет длиной волны 600 нм. Чему равно расстояние

The patient came to see the doctor. he was coughing badly. the doctor said he didn t like the patient s cough and asked him to take off his shirt. he wanted to know how long the patient had had his cough.the doctor asked if the patient took much exercise.the patient said that he didn t do it regularly and explained that he hadn t come about his cough. he said that his feet hurt every time he walked.he had had this pain for two weeks.then he understood that he had had new shoes for 2 weeks too.