## 2 AR/VR Applications
### Industry 4.0  
With the need for a new approach to the modern economy, the concept of Industry 4.0 has been introduced for innovation and technological development in the next industrial revolution by utilizing machines/robots to mimic the work of humans [21]. Industry 4.0 plays a pivotal role in building modern industries with the integration of several disruptive technologies such as the Internet of Things (IoT), machine learning, computing platforms, cyber-security, robotics, simulation, additive manufacturing [22; 23], and AR/VR. The main goals of Industry 4.0 are to apply advanced IT-based technology for mass customization of manufactured products and to foster the adaptive flexibility of the production chain by tracking the growth of parts and products by applying the human-machine interaction (HMI) paradigm [24]. Industry 4.0 makes use of IoT-enabled technology for optimized production in smart factories and develops business models of interaction in the value chain. The technologyperforms the role of a skilled operator such as a robot aided by a machine.  
AR/VR plays an important role in industrial innovations and contributes to their increased growth by bridging the existing gaps between the physical and virtual spaces by allowing people to exist in multiple different realities, mediums, and forms. Recently, investors have accelerated their interest in the AR/VR industry, and it is predicted that the industry will grow by more than USD 125 billion by 2024 [25]. Initially, AR and VR were utilized by retailers for the promotion of their products and services to customers. With the advancement of software algorithms and cutting-edge hardware in AR/VR, they are widely used in industry as a primary resource in supervising and training industry workers to be efficient enough to tackle challenging tasks [26]. In AR, viewers get to experience some prominent scenes of the real world by overlaying the virtual things on real-world objects. AR/VR plays a pivotal role in production growth by enabling a real-time interactive visualization of production line operations and constantly supervising various phenomena affecting them. With the help of extreme computing power and low latency in sensor data provision, processing, analysis, and visual rendering, AR/VR has been able to overcome all the shortcomings of Industry 4.0 [27]. Some of the advantages of AR and VR's usage in Industry 4.0 include their capability to generate a virtual 3D character or the user's avatar by recording his/her physical movements. AR/VR can contribute to the maintenance and repair process by helping workers with the generation of a multimedia-based instruction manual or handbook when they are engaged in some complicated and time-consuming tasks. AR/VR has the capability to increase the work's efficiency and reduce the cognitive load [28] of the workers by assisting them with the display of procedural information using HMDs. Recently, Industry 5.0 has been introduced to complement the Industry 4.0 paradigm with extensive advancement in research for innovative transformation in a human-centric, sustainable, and resilient manner. Industry 5.0 [29] will witness a huge shift from a technology-oriented approach to a human-centric and society-centric approach to improve the decision-making process.