Problem 9: the overall grade in a course is determined from the grades of 5 quizzes, 3 midterms, and a final, using the following scheme: quizzes: quizzes are graded on a scale from 0 to 10. the grade of the lowestquiz is dropped and the average of the 4 quizzes with the higher grades constitutes25% of the course grade. midterms: midterms are graded on a scale from 0 to 100. if the average of themidterm scores is higher than the score on the final, the average of the midtermsis 35% of the course grade. if the final grade is higher than the averageof the midterms, then the lowest midterm isdropped and the average of the two midterms with the higher grades is 35% of the course grade. final: finals are graded on a scale from 0 to 10.the final is 40% of the course grade. write a function that takes quizzes, midterms and finals of students as a matrix and returns another matrix with overall grades and their corresponding letter grades. the rules for letter grades are: a for푔푟푎푑푒푠≥90, b for80≤푔푟푎푑푒푠< 90, c for70≤푔푟푎푑푒푠< 80, d for 60≤푔푟푎푑푒푠< 70, and e for a grade lower than 60. createa script that calls your function for the following two students and prints their overall and letter grades

Infrared sensor is most used sensor in wireless technology where remote controlling functions and detection of surrounding objects/ obstacles are involved. this post will discuss about what is infrared sensor, its working principle, how it works, types, applications, advantages and disadvantages. what is infrared sensor

ir sensor is a simple electronic device which emits and detects ir radiation in order to find out certain objects/obstacles in its range. some of its features are heat and motion sensing.

ir sensors use infrared radiation of wavelength between 0.75 to 1000µm which falls between visible and microwave regions of electromagnetic spectrum. ir region is not visible to human eyes. infrared spectrum is categorized into three regions based on its wavelength i.e. near infrared, mid infrared, far infrared.

wavelength regions of infrared spectrum

near ir – 0.75µm to 3 µm
mid ir – 3 µm to 6 µm
far ir – > 6 µm
1 introduction to infrared sensor

fig. 1 – introduction to infrared sensor

working principle of infrared sensor

infrared sensors works on three fundamental physics laws:

planck’s radiation law: any object whose temperature is not equal to absolute zero (0 kelvin) emits radiation.
stephan boltzmann law: the total energy emitted at all wavelengths by a black body is related to the absolute temperature.
wein’s displacement law: objects of different temperature emit spectra that peak at different wavelengths that is inversely proportional to temperature.
key elements of infrared detection system

the key elements of infrared detection system are:

ir transmitter

ir transmitter acts as source for ir radiation. according to plank’s radiation law, every object is a source of ir radiation at temp t above 0 kelvin. in most cases black body radiators, tungsten lamps, silicon carbide, infrared lasers, leds of infrared wavelength are used as sources.

transmission medium

as the name suggests, transmission medium provides passage for the radiation to reach from ir transmitter to ir receiver. vacuum, atmosphere and optical fibers are used as medium.

ir receiver

generally ir receivers are photo diode and photo transistors. they are capable of detecting infrared radiation. hence ir receiver is also called as ir detector. variety of receivers are available based on wavelength, voltage and package.

ir transmitter and receivers are selected with matching parameters. some of deciding specifications of receivers are photosensitivity or responsivity, noise equivalent power and detectivity.