Opto Electronics » Exercise – 1
1. Consider the following statements
1. LED is also known as direct gap diode
2. LCD generates light
of these statements :
(a) 1 is correct but 2 is wrong
(b) 2 is correct but 1 is wrong
(c) both 1 & 2 are correct
(d) both 1 & 2 are wrong
2. An LED is made up of :
(a) Phosphorescent material
(b) Germanium
(c) Silicon
(d) Gallium arsenide
3. Photoluminescence which persists for some period after excitation is known as :
(a) Phosphorescence
(b) Tri-luminescence
(c) Fluorescence
(d) Bioluminescence
4. In a phototransistor, the base current is :
(a) Set by a bias voltage
(b) Directly proportional to light
(c) Inversely proportional to light
(d) Square to light intensity
5. A photodiode is used in reverse bias because :
(a) Majority of electron-hole pairs swept are reversed across the junction
(b) Only one side is illuminated
(c) Reverse current is small compared to photocurrent
(d) Reverse current is large compared to photocurrent
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