For undergraduate Communication Engineering students. Select the best answer for each question.
1. Who is credited with inventing the first practical electronic television camera tube, the Iconoscope?
a) Philo Farnsworth
b) John Logie Baird
c) Vladimir K. Zworykin
d) Charles Francis Jenkins
2. What physical phenomenon is fundamental to the operation of the Iconoscope camera tube?
a) Photoelectric effect
b) Electromagnetic induction
c) Photoconductivity
d) Thermionic emission
3. The Nipkow disk, used in early mechanical television systems, functioned as:
a) A signal amplifier
b) A mechanical scanning device
c) A photoconductive surface
d) An image storage component
4. In the Iconoscope, what was the purpose of the mosaic screen coated with photoconductive material?
a) To amplify the electron beam
b) To convert light into an electrical charge pattern
c) To filter out unwanted frequencies
d) To synchronize the scanning process
5. Which early television system used a mechanical scanner but an electronic display?
a) The Farnsworth Image Dissector
b) Baird's Televisor
c) The Zworykin Kinescope
d) The EMI electronic camera
6. What was the primary limitation of mechanical television systems like Baird's?
a) Inability to transmit sound
b) Limited resolution and image size
c) Excessive power consumption
d) Lack of synchronization capability
7. What key advantage did electronic television systems have over mechanical ones?
a) Lower production cost
b) Smaller physical size
c) Higher scanning speeds and better image quality
d) Simpler maintenance requirements
8. In early television receivers, what component was used to convert the electronic signal back into a visible image?
a) Photomultiplier tube
b) Cathode ray tube (CRT)
c) Nipkow disk
d) Kerr cell
9. What was the primary function of the electron gun in the Iconoscope?
a) To illuminate the subject
b) To scan the photoconductive mosaic
c) To amplify the video signal
d) To synchronize with the receiver
10. Which improvement in camera tube technology followed the Iconoscope and offered better sensitivity?
a) Orthicon
b) Image Dissector
c) CCD sensor
d) CMOS sensor
Answers and Explanations
1. Correct answer: c) Vladimir K. Zworykin
Vladimir K. Zworykin, while working for RCA, developed the Iconoscope in the 1930s, which became the first practical electronic television camera tube. Though Philo Farnsworth also made significant contributions with his Image Dissector, Zworykin's Iconoscope was more widely adopted in early broadcasting.
2. Correct answer: c) Photoconductivity
Photoconductivity is the phenomenon where a material's electrical conductivity increases when exposed to light. In the Iconoscope, a mosaic of photoconductive elements would discharge when illuminated, creating a charge pattern that corresponded to the image.
3. Correct answer: b) A mechanical scanning device
The Nipkow disk, invented by Paul Nipkow in 1884, was a spinning disk with a spiral pattern of holes that sequentially scanned an image line by line. It was the fundamental component of early mechanical television systems.
4. Correct answer: b) To convert light into an electrical charge pattern
The mosaic screen in the Iconoscope consisted of millions of tiny, isolated photoconductive elements. When light from an image struck this mosaic, each element would discharge proportionally to the light intensity, creating an electrical "image" in the form of a charge pattern.
5. Correct answer: b) Baird's Televisor
John Logie Baird's Televisor system used a mechanical Nipkow disk for scanning the image at the transmitter but used a neon lamp behind a similar disk at the receiver for display, making it a hybrid mechanical-electronic system.
6. Correct answer: b) Limited resolution and image size
Mechanical television systems were fundamentally limited in resolution and image size due to the physical constraints of spinning disks and the limited number of scanning lines that could be practically achieved (typically 30-60 lines).
7. Correct answer: c) Higher scanning speeds and better image quality
Electronic television systems could achieve much higher scanning speeds (allowing for more scan lines and thus higher resolution) and produced significantly better image quality than mechanical systems, which is why they eventually replaced mechanical television entirely.
8. Correct answer: b) Cathode ray tube (CRT)
The cathode ray tube (CRT) was the display technology used in early television receivers. An electron beam would scan across a phosphor-coated screen, causing it to glow where struck, thus reconstructing the transmitted image.
9. Correct answer: b) To scan the photoconductive mosaic
The electron gun in the Iconoscope produced a focused beam of electrons that systematically scanned across the photoconductive mosaic. When the beam hit areas with stored charge (from dark parts of the image), it would replace that charge, generating a signal current.
10. Correct answer: a) Orthicon
The Orthicon (and its improved version, the Image Orthicon) was developed after the Iconoscope and offered significantly better sensitivity, requiring less illumination for adequate image capture. This made studio television production much more practical.