A Faraday cage operates because an external electrical field causes the electric charges within the cage's conducting material to be distributed so that they cancel the field's effect in the cage's interior. This phenomenon is used to protect sensitive electronic equipment (for example RF receivers) from external radio frequency interference (RFI) often during testing or alignment of the device. They are also used to protect people and equipment against actual electric currents such as lightning strikes and electrostatic discharges, since the enclosing cage conducts current around the outside of the enclosed space and none passes through the interior.

Faraday cages cannot block stable or slowly varying magnetic fields, such as the Earth's magnetic field (a compass will still work inside). To a large degree, though, they shield the interior from external electromagnetic radiation if the conductor is thick enough and any holes are significantly smaller than the wavelength of the radiation. For example, certain computer forensic test procedures of electronic systems that require an environment free of electromagnetic interference can be carried out within a screened room. These rooms are spaces that are completely enclosed by one or more layers of a fine metal mesh or perforated sheet metal. The metal layers are grounded to dissipate any electric currents generated from external or internal electromagnetic fields, and thus they block a large amount of the electromagnetic interference. See also electromagnetic shielding. They provide less attenuation of outgoing transmissions than incoming: they can block EMP waves from natural phenomena very effectively, but a tracking device, especially in upper frequencies, may be able to penetrate from within the cage (e.g., some cell phones operate at various radio frequencies so while one frequency may not work, another one will).

The reception or transmission of radio waves, a form of electromagnetic radiation, to or from an antenna within a Faraday cage is heavily attenuated or blocked by the cage; however, a Faraday cage has varied attenuation depending on wave form, frequency, or distance from receiver/transmitter, and receiver/transmitter power. Near-field, high-powered frequency transmissions like HF RFID are more likely to penetrate. Solid cages generally attenuate fields over a broader range of frequencies than mesh cages.

13) A 22-year-old man presents with a solitary 2 cm space-occupying lesion of mixed echogenicity in the right lobe of liver on ultrasound exami- nation. The rest of the liver is normal. Which of the following tests should be done next?

14) A patient presents with acute renal failure and anuria. The USG is normal. Which of the following investigations will give the best information regarding renal function:

Renal DTPA scan is a process for diagnosis and evaluation of kidney functioning. It involves intravenous administration of radiopharmaceutical material to assess the drainage pattern of kidneys and to find out if any area is not functioning properly.

15) A 20-year male patient with 6th cranial nerve palsy on T2 weighted MRI shows a markedly hyperintense lesion in cavernous sinus which shows intense homogenous contrast enhancement. Most probablediagnosisis:

Cavernous sinus hemangiomas (CSHs) are rare, benign extra-axial tumors, primarily affecting middle-aged women. Symptoms vary, but are typically due to mass effect and include headache, vision changes, and cranial nerve palsies.

16) Flowing wax” appearance on anterior and posterior borders of vertebrae with normal intervertebral disc space occurring due to ligament calcification is seen in:

Diffuse idiopathic skeletal hyperostosis (DISH) is a bony hardening of ligaments in areas where they attach to your spine.

Also known as Forestier's disease, this condition might not cause symptoms or require treatment. If it does cause symptoms, the most common are mild to moderate pain and stiffness in your upper back. DISH can also affect your neck and lower back, and some people have DISH in other areas, such as shoulders, elbows, knees and heels.

17) A 7-year-old patient presents with severe headache, paralysis of
upward gaze, loss of light perception and accommodation, nystagmus and failure of convergence. CT scan showed homogenous hyperdense
lesion above the sella and in the
posterior part of the third ventricle.
MRI showed that the lesions were
homogenous and isointense on T1
weighted imaging, and isointense
onT2 weighted imaging with intense contrast enhancement. The most likely diagnosis is:

A germinoma is a type of germ cell tumor commonly found in the brain. Germ cells typically migrate to the gonads during fetal development and become an egg in female ovaries or sperm in male testes.

18) A 35-year-old with a history of
asbestos exposure presents with
chest pain. X-ray shows a solitary
pulmonary nodule in the right lower Zone. CECT reveals an enhancing nodule adjoining the right lower costal pleura with comet tail sign and adjacent pleural thickening. The most likely diagnosis is:

19) A 22-year-old man presents with a solitary 2 cm space-occupying lesion Of mixed echogenicity in the right lobe of liver on ultrasound examination. The rest of the liver is normal. Which of the following tests should be next?

20) A 35-year-old with a history of asbestos exposure presents with chest pain. X-ray shows a solitary pulmonary nodule in the right lower zone. CECT reveals an enhancing nodule adjoining the right lower costal pleura with comet tail sign and adjacent pleural thickening. The most likely diagnosis is: